A Practical Protocol for the Conjugation of Various Amino Acids to Protoporphyrin IX

Abstract

An effective and reliable method was developed for the synthesis of protoporphyrin IX-derived amides. The reaction of protoporphyrin IX with an amino acid [l-leucine, l-valine, l-lysine, l-aspartic acid (Asp), l-glutamic acid (Glu), glycine, or 6-aminohexanoic acid] or a short peptide (Asp-Glu) as an amine counterpart in the presence of O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate and 1H-1,2,3-benzotriazol-1-ol gave the desired diamides in excellent yields.

Protoporphyrin IX (PPIX; Figure [1]) has a unique structure and, as a result, unique chemical, physical, and biological properties. It is a biosynthetic precursor that plays an important role in vital processes such as oxygen transport (hemoglobin) and deposition (myoglobin), electron transfer and transport, catalysis, detoxification, and synthesis of sex hormones (the cytochrome P450 family).[1] The use of PPIX derivatives has also been investigated in diagnostics, treatment of cancers, activation of enzymes, modeling of photosynthesis, and oxygen transport.[2] While working on the synthesis of PPIX-derived regulators of soluble guanylate cyclase,[3] we encountered problems with amidation of the carboxylic acid groups of PPIX.

The chemistry of PPIX has been extensively studied and numerous reports have appeared on structural modifications at the meso positions (formylation, nitration, and cleavage of the porphyrin macrocycle) and at the vinylic groups (reduction, oxidation, addition, substitution, elimi­nation, and metathesis), as well as on conversions of the 13- and 17-(3-alkoxy-3-oxypropyl) groups into ester, amide­, or thioesters groups.[4] Although a variety of protocols are available for the synthesis of PPIX amides, there is no general method for amidation of PPIX with amino acids. The main difficulty encountered in the synthesis of such conjugates is the sensitivity of PPIX toward various reagent, especially those used in subsequent deprotection of polyfunctional amino acids.[5]

Current methodologies for amide bond formation are not always suitable for use with porphyrin-derived acids.[6] The carboxylic groups of PPIX have been activated with various coupling reagents, and the best results were obtained with carbodiimides such as N,N′-dicyclohexylcarbodiimide (DCC) or N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide (EDC) in the presence of 1H-1,2,3-benzotriazol-1-ol (HOBt). Yields of up to 90% were obtained in linking PPIX with β-galactosyl moieties,[7] 1-dodecylamine,[8] triethylene glycol chains,[9] or polyamines.[2c] However, the DCC method was used only in reactions of short peptides with O-succinimide-activated esters of heme, and in these cases yields were 70% or less.[2b] [10]

The formation of a mixed anhydride, a classic method for the synthesis of amides, has also been described.[11] The use of ethyl chloroformate, pivaloyl chloride, or isobutyloxycarbonyl chloride in the presence of a base gives amino acid derivatives or short peptide derivatives of heme in moderate yields (50%); however, in the case of PPIX, the yield was only 10%. As usual, the heme derivative gave better results because of the stabilizing effect of the iron ion in the central core.

Some PPIX amides have been prepared by using coupling reagents based on HOBt. For example, protoporphyrin derivatives containing tyrosine phosphate residues were obtained in moderate yields by using O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HBTU­) with N,N-diisopropylethylamine (DIPEA) as a base,[12] but the process of purification is questionable. HBTU and triethylamine have also been used to couple various peptides or poly(ethylene glycol) derivatives. The same research group also examined the use of (1H-1,2,3-benzotriazol-1-yloxy)(tripyrrolidin-1-yl)phosphonium (PyBOP) as a coupling reagent in the presence of DIPEA­.[2a] These methods gave poly(ethylene glycol) conjugates with PPIX in 70% yield; in the case of peptide conjugates on solid supports, yields of up to 55% were obtained. However, the use of a resin to derivatize PPIX with amino acids or short peptides is sometimes problematic. Replacement of PyBOP with (1H-1,2,3-benzotriazol-1-yloxy)[tris(dimethylamino)]phosphonium (BOP) did not give satisfactory results and only the PPIX monodipeptide was obtained.[13]

Here, we report an effective and general method for the synthesis of PPIX-derived diamides. We selected the reaction of PPIX with l-leucine as our model reaction (Scheme [1]), and examined the reactions of methyl l-leucinate hydrochloride with PPIX in the presence of various coupling agents and bases (Table 1). Because of the low solubility of PPIX in various organic solvents, all the reactions were performed in N,N-dimethylformamide. EDC is generally used in peptide synthesis; however, in our case, the reactions performed in the presence of EDC did not give satisfactory results, regardless of the amine used, the presence or absence of HOBt, the reaction temperature (25–60 °C), or the time (18–48 hours) (Table 1, entries 2–6).

We then studied several other coupling reagents, including 1,1′-carbonyldiimidazole (CDI), diisopropylcarbodiimide (DIC), 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM), and HBTU (entries 1 and 7–9). The best results were obtained when HBTU was used in the presence of HOBt (entry 9). Changing the base from triethylamine to DIPEA led to an appreciable increase in the yield from 82% to 97% (entries 9 and 10). Therefore, the best conditions for the reaction are PPIX (1 equiv), amino acid (6 equiv), HBTU (3 equiv), HOBt (4 equiv), and DIPEA (4 equiv) in N,N-dimethylformamide as solvent at room temperature, with a reaction time of 18 hours (entry 10).

Having tuned the reaction conditions, we tested the utility of our protocol with several amino acids chosen for the properties of their side chains: hydrophobic (valine, leucine), negative electrical charge (aspartic acid or glutamic acid), or positive electrical charge (lysine). A series of conjugates 2–7 were obtained in satisfactory yields (Scheme [2]).

We then attempted to remove the protecting groups from the amino and carboxyl groups in compounds 1–7 (Table 2). Hydrolysis of methyl esters with lithium hydroxide at 0 °C for 24 hours gave traces of desired salt 9. Extending the reaction time and increasing the temperature to 60 °C led to decomposition of the diamide 1. We therefore attempted hydrolysis of methyl ester 1 with sodium hydroxide in a mixture of methanol and dichloromethane at room temperature for two hours and we obtained the corresponding disodium salt 9 in 95% yield (entry 1). The diamide disodium salts 10–15 and 17 were obtained in a similar manner (entries 2–7 and 9, respectively).

Purification of the deprotected porphyrins 9–15 turned out to be problematic, as they decomposed upon chromatography. Therefore, purification was limited to precipitation followed by washing with a small amount of water. In almost all cases, yields of the disodium salts 9–15 were quantitative (entry 1–7). We also examined the subsequent deprotection of the tert-butoxycarbonyl group in derivative 7. Methods for this reaction differ mostly in terms of the concentration of trifluoroacetic acid, the type of scavenger, and the reaction time. The use of 50% tri­fluoroacetic acid in dichloromethane with triethylsilane as the scavenger gave disappointing results. However, by increasing the concentration of trifluoroacetic acid to 85% and using anisole as a scavenger, we obtained the desired product 16 quantitatively (entry 8). This product was precipitated with diethyl ether and washed with diethyl ether to remove the trifluoroacetic acid completely.

We also used our method to synthesize a diamide in which a short peptide (aspartylglutamic acid trimethyl ester) was conjugated to PPIX. The HBTU–HOBt–DIPEA system gave the coupled compound 8 in 60% yield (Scheme [2]). Unfortunately, coupling with dipeptides containing glycine as the N-terminal amino acid led mixtures of products. Deprotection of porphyrin 8 with sodium hydroxide worked well and gave the derivative 17 in 86% yield (Table 2, entry 9). The structures and purities of all the products were confirmed by NMR spectroscopy and by mass spectroscopy.

In summary, we have developed an effective and reliable protocol for the synthesis of PPIX-derived diamides containing residues of valine, leucine, aspartic acid, glutamic acid, lysine, or a short peptide (aspartylglutamic acid). The use of the HBTU–HOBt–DIPEA system for coupling, sodium hydroxide for hydrolysis, and trifluoroacetic acid–anisole for tert-butoxycarbonyl group deprotection gave excellent results in almost all cases.

Unless otherwise noted, all commercially available starting materials were used directly without further purification. Reactions under anhyd conditions were performed in anhyd distilled solvents under an atmosphere of argon and in darkness (Al foil). All reactions were monitored by TLC using 0.20-mm plates of silica gel F₂₅₄ or RP-18 F₂₅₄S. Dry-column vacuum chromatography (DCVC) was performed by using silica gel (200–300 mesh). ¹H and ¹³C NMR were recorded on Bruker and Variant spectrometers operating at 500 MHz (¹H) or 125 MHz (¹³C). Chemical shifts are reported relative to TMS as the internal standard for ¹H (δ = 0 ppm) and to the central line of the deuterated solvent for ¹³C (CDCl₃: δ = 77.0 ppm; DMSO-d ₆: δ = 39.5 ppm; TFA-d ₁: δ = 116.6, 164.2 ppm). Electronic absorption spectra were measured on a PerkinElmer Lambda 35 UV/vis spectrophotometer. Mass spectra were obtained at the LCU Mass Spectra Facility. Methyl esters of amino acids and dipeptide were prepared in quantitative yields by standard procedures.[14] The methyl ester of N-Boc-N′-Cbz-lysine was obtained by the HBTU method,[15] and Cbz deprotection was carried out by using a known procedure.[16]

Amino Acid and Peptide Derivatives of PPIX 1–8; General Procedure

HBTU (3.0 equiv, 60 mg, 0.16 mmol), HOBt (4.0 equiv, 29 mg, 0.21 mmol), and DIPEA (4.0 equiv, 37 μL, 0.21 mmol) were added to a mixture of protoporphyrin IX (30 mg, 0.05 mmol), and the appropriate amino acid or peptide methyl ester hydrochloride (6.0 equiv, 0.32 mmol) in anhyd DMF (4 mL). The resulting mixture was stirred overnight at r.t. and then poured into CH₂Cl₂ and washed sequentially with aq HCl (50 mL), sat. aq NaHCO₃ (50 mL), H₂O (2 × 50 mL), and brine (50 mL). The organic layer was dried (Na₂SO₄), filtered, and concentrated, and the crude solid was purified by dry-column vacuum chromatography.

Dimethyl (2S,2′S)-2,2′-{(2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl)bis[(1-oxopropane-3,1-diyl)imino]}bis(4-methylpentanoate) (1)

Compound 1 was prepared from protoporphyrin IX (30 mg, 0.05 mmol) by following the general procedure. The crude product was purified by DCVC (2% MeOH–CH₂Cl₂) and crystallization (hexane–CH₂Cl₂) to give a red solid: yield: 42 mg (97%); R_f  = 0.48 (5% MeOH–CH₂Cl₂).

¹H NMR (500 MHz, CDCl₃): δ = 10.00 (s, 1 H, meso), 9.93 (s, 1 H, meso), 9.89 (s, 1 H, meso), 9.79 (s, 1 H, meso), 8.23–8.17 [m, 2 H, –CH= (vinyl)], 6.73 (dd, J = 7.9, 23.4 Hz, 2 H, –NH–), 6.33 [d, J = 17.8, 2 H, =CH₂ (vinyl)], 6.16 [d, J = 11.4 Hz, 2 H, =CH₂ (vinyl)], 4.38–4.24 (m, 6 H, por–CH₂–, –CH–), 3.63–3.61 (m, 6 H, por–CH₃), 3.52–3.51 (m, 6 H, por–CH₃), 3.15–3.03 (m, 4 H, –CH₂ –CONH–), 2.96 (m, 6 H, –COOCH₃), 1.06–0.99 (m, 2 H, –CH₂–), 0.96–0.92 (m, 2 H, –CH₂–), 0.79–0.69 [m, 2 H, –CH(CH₃)₂], 0.11–0.03 (m, 12 H, –CH₃), –4.29 (s, 2 H, NH).

¹³C NMR (125 MHz, CDCl₃): δ = 172.9, 172.8, 172.7, 172.6, 136.2, 130.2, 120.3, 97.3, 96.7, 96.5, 96.4, 51.5, 50.5, 40.7, 39.6, 24.0, 23.9, 22.9, 22.0, 21.9, 21.1, 21.0, 12.6, 12.5, 11.5, 11.4.

UV/Vis (CH₂Cl₂): λ_max (ε) = 406 (1.61 × 10⁵), 504 (1.34 × 10⁴), 540 (1.04 × 10⁴), 574 (6.59 × 10³), 630 nm (4.94 × 10³).

HRMS-ESI: m/z [M + Na]⁺ calcd for C₄₈H₆₀N₆NaO₆: 839.4498; found: 839.4467.

Anal. Calcd for C₄₈H₆₀N₆O₆ + H₂O: C, 69.04; H, 7.48; N, 10.06. Found: C, 69.16; H, 7.35; N, 9.98.

Dimethyl (2S,2′S)-2,2′-{(2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl)bis[(1-oxopropane-3,1-diyl)imino]}bis(3-methylbutanoate) (2)

Compound 2 was prepared from protoporphyrin IX (30 mg, 0.05 mmol) by following the general procedure. The crude product was purified by DCVC (2% MeOH–CH₂Cl₂) and crystallization (hexane–CH₂Cl₂) to give a red solid: yield: 34 mg (81%); R_f  = 0.52 (3% MeOH–CH₂Cl₂).

¹H NMR (500 MHz, CDCl₃): δ = 10.11 (s, 1 H, meso), 10.04 (s, 1 H, meso), 10.01 (s, 1 H, meso), 9.94 (s, 1 H, meso), 8.28–8.22 [m, 2 H, –CH= (vinyl)], 6.79–6.77 (m, 2 H, –NH–), 6.36 [d, J = 17.8 Hz, 2 H, =CH₂ (vinyl)], 6.18 [d, J = 11.5 Hz, 2 H, =CH₂ (vinyl)], 4.37 (t, J = 7.6 Hz, 4 H, por–CH₂–), 4.25–4.22 (m, 2 H, –CH–), 3.67 (m, 6 H, por–CH₃), 3.58 (s, 6 H, por–CH₃), 3.20–3.10 (m, 4 H, –CH₂ –CONH–), 2.77 (s, 3 H, –COOCH₃), 2.75 (s, 3 H, –COOCH₃), 1.66–1.59 [m, 2 H, –CH(CH₃)₂], 0.45 (dd, J = 2.1, 6.7 Hz, 6 H, –CH₃), 0.31 (t, J = 5.9 Hz, 6 H, –CH₃), –4.08 (s, 2 H, NH).

¹³C NMR (125 MHz, CDCl₃): δ = 172.8, 171.7, 130.2, 120.7, 97.6, 97.0, 96.8, 96.7, 57.3, 51.2, 39.6, 30.6, 23.1, 18.3, 17.6, 12.7, 11.6, 11.5.

UV/Vis (CH₂Cl₂): λ_max (ε) = 406 (1.26 × 10⁵), 505 (1.09 × 10⁴), 540 (8.90 × 10³), 574 (5.09 × 10³), 629 nm (4.49 × 10³).

HRMS-ESI: m/z [M + Na]⁺ calcd for C₄₆H₅₆N₆NaO₆: 811.4176; found: 811.4154.

Anal. Calcd for C₄₆H₅₆N₆O₆ + H₂O: C, 69.24; H, 7.24; N, 10.53. Found: C, 69.37; H, 7.40; N, 10.61.

Tetramethyl (2S,2′S)-2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}disuccinate (3)

Compound 3 was prepared from protoporphyrin IX (30 mg, 0.05 mmol) by following the general procedure. The crude product was purified by DCVC (2% MeOH–CH₂Cl₂) and crystallization (hexane–CH₂Cl₂) to give a red solid: yield: 36 mg (79%); R_f  = 0.57 (10% MeOH–CH₂Cl₂).

¹H NMR (500 MHz, CDCl₃): δ = 9.90 (s, 1 H, meso), 9.85 (s, 1 H, meso), 9.79 (s, 1 H, meso), 9.69 (s, 1 H, meso), 8.20–8.13 [m, 2 H, –CH= (vinyl)], 7.08–7.05 (m, 2 H, –NH–), 6.32 [dd, J = 17.8, 2.8 Hz, 2 H, =CH₂ (vinyl)], 6.15 [d, J = 11.4 Hz, 2 H, =CH₂ (vinyl)], 4.60–4.56 (m, 2 H, –CH–), 4.39–4.31 (m, 2 H, por–CH₂–), 4.27–4.20 (m, 2 H, por–CH₂–), 3.59 (s, 3 H, por–CH₃), 3.57 (s, 3 H, por–CH₃), 3.49 (s, 3 H, por–CH₃), 3.47 (s, 3 H, por–CH₃), 3.19–3.15 (m, 8 H, –COOCH₃, –CH₂ –CONH–), 3.07–3.01 (m, 2 H, –CH₂ –CONH–), 2.24–2.19 (m, 8 H, –COOCH₃, –CH₂–), 1.66–1.59 (m, 2 H, –CH₂–), –4.52 (s, 2 H, NH).

¹³C NMR (125 MHz, CDCl₃): δ = 172.5, 170.8, 170.49, 170.47, 138.2, 136.2, 130.2, 130.1, 120.5, 97.37, 97.36, 96.89, 96.88, 96.6, 96.51, 96.50, 52.1, 50.6, 50.5, 48.06, 48.05, 39.2, 35.1, 22.8, 12.7, 12.6, 11.5, 11.4.

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₆H₅₃N₆O₁₀: 849.3817; found: 849.3809.

UV/Vis (CH₂Cl₂): λ_max (ε) = 406 (1.2 × 10⁵), 505 (1.05 × 10⁴), 541 (7.50 × 10³), 574 (4.50 × 10³), 630 nm (3.00 × 10³).

Anal. Calcd for C₄₆H₅₂N₆O₁₀ + 0.5 H₂O: C, 64.40; H, 6.23; N, 9.80. Found: C, 64.36; H, 6.33; N, 9.71.

Tetramethyl 2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}dipentanedioate (4)

Compound 4 was prepared from protoporphyrin IX (30 mg, 0.05 mmol) by following the general procedure. The crude product was purified by DCVC (2% MeOH–CH₂Cl₂) and crystallization (hexane–CH₂Cl₂) to give a red solid: yield: 36 mg (77%); R_f  = 0.62 (5% MeOH–CH₂Cl₂).

¹H NMR (500 MHz, CDCl₃): δ = 9.79 (s, 1 H, meso), 9.75 (s, 1 H, meso), 9.69 (s, 1 H, meso), 9.57 (s, 1 H, meso), 8.15–8.06 [m, 2 H, –CH= (vinyl)], 7.05 (t, J = 7.8 Hz, 2 H, –NH–), 6.32–6.26 [m, 2 H, =CH₂ (vinyl)], 6.16–6.12 [m, 2 H, =CH₂ (vinyl)], 4.28–4.22 (m, 6 H, –CH–, por–CH₂–), 3.53–3.52 (m, 6 H, por–CH₃), 3.45–3.41 (s, 6 H, por–CH₃), 3.11–3.02 (m, 10 H, –CH₂ –CONH–, –COOCH₃), 2.97 (s, 6 H, –COOCH₃), 1.67–1.41 (m, 8 H, –CH₂–CH₂–), –4.81 (br s, 1 H, NH).

¹³C NMR (125 MHz, CDCl₃): δ = 172.9, 172.6, 172.5, 171.7, 130.0, 138.2, 136.1, 120.4, 97.2, 96.6, 96.3, 96.2, 51.7, 51.52, 51.50, 51.02, 51.00, 39.3, 29.18, 29.16, 26.5, 26.4, 22.8, 12.6, 12.5, 11.4, 11.3.

UV/Vis (CH₂Cl₂): λ_max (ε) = 406 (1.53 × 10⁵), 505 (1.35 × 10⁴), 541 (1.05 × 10⁴), 576 (6.14 × 10³), 629 nm (4.64 × 10³).

HRMS-ESI: m/z [M + Na]⁺ calcd for C₄₈H₅₆N₆NaO₁₀: 899.3954; found: 899.3950.

Anal. Calcd for C₄₈H₅₆N₆O₁₀: C, 65.74; H, 6.44; N, 9.58. Found: C, 65.81; H, 6.46; N, 9.47.

Dimethyl 2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}diacetate (5)

Compound 5 was prepared from protoporphyrin IX (30 mg, 0.05 mmol) by following the general procedure. The crude product was purified by DCVC (5% MeOH–CH₂Cl₂) and crystallization (hexane–CH₂Cl₂) to give a red solid: yield: 28 mg (74%); R_f  = 0.57 (10% MeOH–CH₂Cl₂).

¹H NMR (500 MHz, CDCl₃): δ = 10.24–10.19 (m, 3 H, meso), 10.11 (s, 1 H, meso), 8.34–8.26 [m, 2 H, –CH= (vinyl)], 7.01 (br s, 2 H, –NH–), 6.41–6.38 [m, 2 H, =CH₂ (vinyl)], 6.21–6.20 [m, 2 H, =CH₂ (vinyl)], 4.44 (br s, 4 H, por–CH₂–), 3.87 (br s, 4 H, –CH₂–), 3.73–3.65 (m, 12 H, por–CH₃), 3.36 (s, 6 H, –COOCH₃), 3.20 (br s, 4 H, –CH₂ –CONH–), –3.69 (s, 2 H, NH).

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₀H₄₅N₆O₆: 705.3395; found: 705.3373.

UV/Vis (CH₂Cl₂): λ_max (ε) 406 (1.45 × 10⁵), 505 (1.20 × 10⁴), 541 (5.89 × 10³), 576 (6.00 × 10³), 630 nm (4.50 × 10³).

Anal. Calcd for C₄₀H₄₄N₆O₆ + H₂O: C, 66.46; H, 6.41; N, 11.63. Found: C, 66.78; H, 6.36; N, 11.54.

Dimethyl 6,6′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}dihexanoate (6)

Compound 6 was prepared from protoporphyrin IX (30 mg, 0.05 mmol) by following the general procedure. The crude product was purified by DCVC (2% MeOH–CH₂Cl₂) and crystallization (hexane–CH₂Cl₂) to give a red solid: yield: 34 mg (79%); R_f  = 0.46 (5% MeOH–CH₂Cl₂).

¹H NMR (500 MHz, CDCl₃): δ = 9.66 (s, 1 H, meso), 9.62 (s, 1 H, meso), 9.50 (m, 2 H, meso), 8.09–8.03 [m, 1 H, –CH= (vinyl)], 7.91–7.85 [m, 1 H, –CH= (vinyl)], 6.88 (br s, 1 H, –NH–), 6.81 (br s, 1 H, –NH–), 6.26–6.04 [m, 4 H, =CH₂ (vinyl)], 4.09 (br s, 4 H, por–CH₂–), 3.46–3.45 (m, 9 H, por–CH₃), 3.35–3.34 (m, 6 H, por–CH₃, –COOCH₃), 3.30 (s, 3 H, –COOCH₃), 2.96–2.89 (m, 8 H, –CH₂ –CONH–, –CH₂–), 1.56–1.48 (m, 4 H, –CH₂–), 0.97–0.85 (m, 8 H, –CH₂–), 0.72–0.61 (m, 4 H, –CH₂–), –4.90 (s, 1 H).

¹³C NMR (125 MHz, CDCl₃): δ = 173.67, 173.65, 172.7, 138.9, 136.0, 129.8, 129.6, 120.6, 120.5, 96.9, 96.4, 96.3, 96.1, 51.23, 51.22, 39.7, 39.1, 33.24, 33.20, 28.6, 28.5, 25.9, 25.8, 23.94, 23.90, 23.0, 22.9, 12.4, 12.3, 11.3, 11.2.

UV/Vis (CH₂Cl₂): λ_max (ε) = 406 (1.40 × 10⁵), 505 (1.19 × 10⁴), 540 (8.90 × 10⁴), 577 (5.30 × 10³), 630 nm (3.89 × 10³).

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₈H₆₁N₆O₆: 817.4663; found: 817.4647.

Anal. Calcd for C₄₈H₆₀N₆O₆: C, 70.56; H, 7.40; N, 10.26. Found: C, 70.53; H, 7.39; N, 10.08.

Dimethyl (2S,2′S)-2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}bis{6-[(tert-butoxycarbonyl)amino]hexanoate}(7)

Compound 7 was prepared from protoporphyrin IX (30 mg, 0.05 mmol) by following the general procedure. The crude product was purified by DCVC (2% MeOH–CH₂Cl₂) and crystallization (hexane–CH₂Cl₂) to give red solid: yield: 49 mg (87%); R_f  = 0.75 (5% MeOH–CH₂Cl₂).

¹H NMR (500 MHz, CDCl₃): δ = 9.86 (s, 1 H, meso), 9.78 (s, 1 H, meso), 9.74 (s, 1 H, meso), 9.62 (s, 1 H, meso), 8.18–8.11 [m, 2 H, –CH= (vinyl)], 6.90 (br s, 2 H, –NH–), 6.33 [d, J = 17.5 Hz, 2 H, =CH₂ (vinyl)], 6.17 [d, J = 11.5 Hz, 2 H, =CH₂ (vinyl)], 4.39 (br s, 2 H, –CH–), 4.22 (br s, 4 H, por–CH₂–), 3.59–3.56 (m, 6 H, por–CH₃), 3.49–3.47 (m, 6 H, por–CH₃), 3.34 (s, 6 H, –COOCH₃), 3.19 (br s, 2 H, –CH₂ –CONH–), 2.96–2.89 (m, 2 H, –CH₂ –CONH–), 2.42 (br s, 1 H, –CHH-), 1.71 (br s, 1 H, –CH₂–), 1.48 (br s, 2 H, –CH₂–), 1.22 (br s, 20 H, –CH₂–, –C(CH₃)₃], 0.79 (br s, 3 H, –CH₂–), 0.57 (br s, 2 H, –CH₂–), 0.12 (br s, 3 H, –CH₂–), 0.39 [br s, 1 H, –CHH–), 0.95 (br s, 1 H, –CHH–), –4.90 (br s, 2 H, NH).

¹³C NMR (125 MHz, CDCl₃): δ = 172.5, 172.4, 155.1, 138.5, 135.9, 130.2, 130.1, 120.6, 97.2, 96.8, 96.7, 96.3, 78.3, 51.9, 51.7, 39.4, 38.4, 30.8, 28.2, 28.0, 23.1, 20.8, 12.7, 12.6, 11.5, 11.4.

HRMS-ESI: m/z [M + Na]⁺ calcd for C₅₈H₇₈N₈NaO₁₀: 1069.5746; found: 1069.5733.

UV/Vis (CH₂Cl₂): λ_max (ε) = 406 (1.59 × 10⁵), 504 (1.22 × 10⁴), 541 (1.06 × 10⁴), 574 (7.19 × 10³), 630 (4.24 × 10³), 667 nm (1.45 × 10³).

Anal. Calcd for C₅₈H₇₈N₈O₁₀: C, 66.52; H, 7.51; N, 10.7. Found: C, 66.50; H, 7.50; N, 10.52.

Tetramethyl 2,2′-([2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis{(1-oxopropane-3,1-diyl)imino[(2S)-4-meth­oxy-1,4-dioxobutane-2,1-diyl]imino})dipentanedioate (8)

Compound 8 was prepared from protoporphyrin IX (30 mg, 0.05 mmol) by following the general procedure. The crude product was purified by DCVC (2% MeOH–CH₂Cl₂) and crystallization (hexane–CH₂Cl₂) to give a red solid; yield: 36.5 mg (60%); R_f  = 0.62 (5% MeOH–CH₂Cl₂).

¹H NMR (500 MHz, CDCl₃): δ = 9.94 (m, 2 H, meso), 9.91 (s, 1 H, meso), 9.78 (s, 1 H, meso), 8.21–8.14 [m, 2 H, –CH= (vinyl)], 7.29–7.27 (m, 2 H, –NH–), 7.02 (d, J = 7.8, 2 H, –NH–), 6.33 [dd, J = 6.3, 1.8 Hz, 2 H, =CH₂ (vinyl)], 6.17 [d, J = 11.4 Hz, 2 H, =CH₂ (vinyl)], 4.67–4.62 (m, 2 H, –CH–), 4.45–4.38 (m, 2 H, por–CH₂–), 4.34–4.29 (m, 2 H, por–CH₂–), 4.09–4.04 (m, 2 H, –CH–), 3.60 (s, 6 H, por–CH₃), 3.55–3.54 (m, 6 H, por–CH₃), 3.46–3.41 (m, 12 H, –COOCH₃), 3.28–3.22 (m, 2 H, –CH₂ –CONH–), 3.08–3.02 (m, 2 H, –CH₂ –CONH–), 2.72 (s, 3 H, –COOCH₃), 2.70 (s, 3 H, –COOCH₃), 2.16–2.11 (m, 2 H, –CH₂–), 2.05–1.93 (m, 4 H, –CH₂–), 1.79–1.68 (m, 4 H, –CH₂–), 1.57–1.50 (m, 2 H, –CH₂–), –4.08 (br s, 1 H, NH).

¹³C NMR (125 MHz, CDCl₃): δ = 173.0, 172.99, 172.96, 171.3, 171.2, 170.1, 136.4, 130.0, 120.8, 97.6, 97.1, 96.7, 96.4, 52.1, 51.5, 51.09, 51.06, 49.0, 39.3, 35.1, 35.0, 31.5, 29.6, 26.4, 22.7, 22.6, 14.0, 12.64, 12.61, 11.59, 11.56.

HRMS-ESI: m/z [M + H]⁺ calcd for C₅₈H₇₁N₈O₁₆: 1135.4988; found: 1135.4987.

UV/Vis (CH₂Cl₂): λ_max (ε) = 405 (2.65 × 10⁵), 506 (2.24 × 10⁴), 540 (1.67 × 10⁴), 577 (1.04 × 10⁴), 629 nm (8.05 × 10³).

Anal. Calcd for C₅₈H₇₀N₈O₁₆: C, 61.36; H, 6.22; N, 9.87. Found: C, 61.31; H, 6.48; N, 9.68.

Carboxylic Acid Sodium Salts 9–16; General Procedure

The appropriate methyl ester 1–7 was dissolved in CH₂Cl₂ (4 mL) and the soln was heated to 40 °C. MeOH (4 mL) followed by 4 M aq NaOH (2 mL) were added and the mixture was refluxed until the reaction was complete (TLC, ~3 h). The organic volatile compounds were removed under reduced pressure and the suspension was placed in a vial for subsequent centrifugation.

Disodium (2S,2′S)-2,2′-{(2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl)bis[(1-oxopropane-3,1-diyl)imino]}bis(4-methylpentanoate) (9)

Compound 9 was prepared from diamide 1 (50 mg, 0.06 mmol) by following the general procedure. The product, which was slightly soluble in H₂O, was washed several times with H₂O and then with Et₂O to give a dark-red solid; yield: 48 mg (95%); mp > 400 °C; R_f  = 0.67 (MeOH).

¹H NMR (500 MHz, TFA-d ₁): δ = 11.17–11.06 (m, 4 H, meso), 8.42–8.31 [m, 2 H, –CH= (vinyl)], 6.72–6.66 [m, 2 H, =CH₂ (vinyl­)], 6.51–6.45 [m, 2 H, =CH₂ (vinyl)], 4.84 (br s, 4 H, por–CH₂–), 4.56 (br s, 2 H, –CH–), 3.94–3.84 (m, 12 H, por–CH₃), 3.44–3.33 (m, 4 H, –CH₂ –CONH–), 1.52–1.40 [m, 6 H, –CH(CH₃)₂, –CH₂–], 0.90–0.82 (m, 12 H, –CH₃).

¹³C NMR (125 MHz, TFA-d ₁): δ = 177.8, 176.4, 142.6, 142.3, 142.2, 142.1, 141.7, 141.6, 141.23, 141.20, 140.9, 140.1, 140.0, 139.7, 128.2, 126.9, 100.9, 100.1, 99.9, 98.1, 51.9, 39.2, 37.0, 29.3, 24.5, 22.1, 20.9, 19.6, 11.0, 10.7.

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₆H₅₇O₆N₆: 789.4334; found: 789.4347.

UV/Vis (DMSO): λ_max (ε) = 408 (1.53 × 10⁵), 506 (1.40 × 10⁴), 541 (1.12 × 10⁴), 575 (7.06 × 10³), 630 (5.05 × 10³), 669 nm (7.01 × 10²).

Disodium (2S,2′S)-2,2′-{(2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl)bis[(1-oxopropane-3,1-diyl)imino]}bis(3-methylbutanoate) (10)

A soln of diamide 2 (20 mg, 0.02 mmol) in CH₂Cl₂ (2 mL) was heated to 40 °C. MeOH (2 mL) followed by 4 M aq NaOH (1 mL) were added and the mixture was refluxed until the reaction was complete (TLC, ~3 h). The volatile organic compounds were removed under reduced pressure and the resulting suspension was placed in a vial for subsequent centrifugation. The product, which was slightly soluble in H₂O was washed several times with H₂O and then with Et₂O to give a dark-red solid; yield: 18 mg (88%); mp > 400 °C; R_f  = 0.73 (MeOH).

¹H NMR (500 MHz, TFA-d ₁): δ = 11.01 (m, 2 H, meso), 10.95–10.94 (m, 2 H, meso), 8.26–8.16 [m, 2 H, –CH= (vinyl)], 6.56–6.52 [m, 2 H, =CH₂ (vinyl)], 6.36–6.30 [m, 2 H, =CH₂ (vinyl)], 4.68 (br s, 4 H, por–CH₂–), 4.35 (br s, 2 H, –CH–), 3.78–3.68 (m, 12 H, por–CH₃), 3.27–3.23 (m, 4 H, –CH₂ –CONH–), 1.95 [br s, 2 H, –CH(CH₃)₂], 0.78–0.70 (m, 12 H, –CH₃).

¹³C NMR (125 MHz, TFA-d ₁): δ = 176.6, 176.4, 142.5, 142.3, 142.1, 141.7, 141.6, 141.1, 140.9, 140.24, 142.20, 140.1, 139.8, 139.7, 128.3, 128.2, 126.9, 126.8, 100.9, 99.9, 99.8, 98.3, 58.9, 36.8, 30.2, 22.2, 17.1, 16.2, 11.0, 10.6.

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₄H₅₃N₆O₆: 761.4021; found: 761.4020.

UV/Vis (DMSO): λ_max (ε) = 408 (1.41 × 10⁵), 505 (1.28 × 10⁴), 541 (1.04 × 10⁴), 575 (6.61 × 10³), 630 (4.63 × 10³), 669 nm (1.04 × 10³).

Tetrasodium (2S,2′S)-2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}disuccinate (11)

A soln of diamide 3 (30 mg, 0.03 mmol) in CH₂Cl₂ (2 mL) was heated to 40 °C. MeOH (2 mL) followed by 4 M aq NaOH (1 mL) were added and the mixture was refluxed until the reaction was complete (TLC, ~3 h). Volatile organic compounds were removed under reduced pressure and the residue was crystallized (H₂O/MeOH) and then washed several times with MeOH and then with Et₂O to give a red solid; yield: 30 mg (96%); mp > 400 °C; R_f  = 0.78 (MeOH–H₂O–Et₃N, 3:1:1).

¹H NMR (500 MHz, TFA-d ₁): δ = 11.11 (s, 2 H, meso), 11.05–11.04 (m, 2 H, meso), 8.33–8.26 [m, 2 H, –CH= (vinyl)], 6.63 [dd, J = 11.5, 8.4 Hz, 2 H, =CH₂ (vinyl)], 6.43 [dd, J = 17.7, 5.3 Hz, 2 H, =CH₂ (vinyl)], 4.77 (br s, 6 H, por–CH₂–, –CH–), 3.87 (s, 3 H, por–CH₃), 3.84–3.83 (m, 6 H, por–CH₃), 3.80 (s, 3 H, por–CH₃), 3.32–3.26 (m, 4 H, –CH₂ –CONH–), 2.77–2.69 (m, 2 H, –CH₂–), 2.59–2.46 (m, 2 H, –CH₂–).

¹³C NMR (125 MHz, TFA-d ₁): δ = 177.9, 177.8, 177.7, 176.9, 144.7, 144.5, 144.3, 144.2, 143.7, 143.6, 143.3, 143.2, 143.1, 142.34, 142.31, 142.2, 142.1, 142.0, 141.9, 130.4, 130.3, 129.1, 129.0, 102.9, 102.1, 101.9, 100.6, 68.3, 50.8, 38.8, 38.7, 36.5, 24.24, 24.22, 14.7, 13.19, 13.18, 12.74, 12.74.

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₂H₄₅O₁₀N₆: 793.3197; found: 793.3190.

UV/Vis (10% aq HCl): λ_max (ε) = 411 (2.45 × 10⁵), 557 (1.5 × 10⁴), 603 nm (5.00 × 10³).

Tetrasodium 2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}dipentanedioate (12)

Compound 12 was prepared from diamide 4 (60 mg, 0.06 mmol) by following the general procedure. Crystallization (H₂O–MeOH) followed by washing several times with MeOH and then with Et₂O gave a red solid; yield: 49 mg (79%); mp > 400 °C; R_f  = 0.81 (MeOH–H₂O–Et₃N, 3:1:1).

¹H NMR (500 MHz, TFA-d ₁): δ = 11.22–11.15 (m, 4 H, meso), 8.45–8.37 [m, 2 H, –CH= (vinyl)], 6.74 [dd, J = 11.3, 9.7 Hz, 2 H, =CH₂ (vinyl)], 6.53 [dd, J = 17.4, 4.8 Hz, 2 H, =CH₂ (vinyl)], 4.90–4.80 (m, 4 H, por–CH₂–, –CH–), 4.74–4.70 (m, 2 H, por–CH₂–), 3.99 (s, 3 H, por–CH₃), 3.95 (s, 3 H, por–CH₃), 3.93 (s, 3 H, por–CH₃), 3.90 (s, 3 H, por–CH₃), 3.52–3.32 (m, 4 H, –CH₂ –CONH–), 2.60–2.50 (m, 4 H, –CH₂–), 2.28–2.19 (m, 2 H, –CH₂–), 2.00–1.89 (m, 2 H, –CH₂–).

¹³C NMR (125 MHz, TFA-d ₁): δ = 181.4, 178.2, 144.7, 144.5, 144.3, 144.2, 143.8, 143.7, 143.3, 143.2, 143.2, 143.1, 142.4, 142.3, 142.2, 142.0, 141.9, 141.8, 130.4, 130.3, 129.05, 129.00, 102.9, 102.1, 101.9, 100.3, 54.2, 39.1, 39.0, 31.3, 27.5, 27.4, 24.1, 13.1, 12.8, 12.7.

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₄H₄₉N₁₀O₆: 821.3510; found: 821.3506.

UV/Vis (10% aq HCl): λ_max (ε) = 411 (3.80 × 10⁵), 557 (2.44 × 10⁴), 604 nm (9.25 × 10³).

Disodium 2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}diacetate (13)

Compound 13 was prepared from diamide 5 (34 mg, 0.05 mmol) by following the general procedure. The product, which was slightly soluble in H₂O, was washed several times with H₂O and then with Et₂O to give a red solid; yield: 32 mg (91%); mp > 400 °C; R_f  = 0.54 (MeOH–H₂O–Et₃N, 3:1:1).

¹H NMR (500 MHz, TFA-d ₁): δ = 11.01–11.00 (m, 2 H, meso), 10.95 (s, 1 H, meso), 10.94 (s, 1 H, meso), 8.24–8.16 [m, 2 H, –CH= (vinyl)], 6.55 [dd, J = 11.5, 8.2 Hz, 2 H, =CH₂ (vinyl)], 6.33 [d, J = 17.7 Hz, 2 H, =CH₂ (vinyl)], 4.70–4.66 (m, 4 H, por–CH₂–), 3.83–3.81 (m, 4 H, –CH₂–), 3.78 (s, 3 H, por–CH₃), 3.74 (s, 3 H, por–CH₃), 3.72 (s, 3 H, por–CH₃), 3.69 (s, 3 H, por–CH₃), 3.23–3.17 (m, 4 H, por–CH₂–).

¹³C NMR (125 MHz, TFA-d ₁): δ = 178.7, 176.8, 144.7, 144.4, 144.2, 143.9, 143.8, 143.34, 143.31, 143.2, 143.0, 142.3, 142.2, 142.0, 141.9, 141.8, 130.4, 130.3, 129.1, 129.0, 102.9, 102.1, 101.9, 100.4, 43.0, 39.0, 38.9, 24.1, 13.1, 12.74, 12.73.

HRMS-ESI: m/z [M + H]⁺ calcd for C₃₈H₄₁N₆O₆: 677.3082; found: 677.3103.

UV/Vis (10% HCl in H₂O): λ_max (ε) = 410 (2.7 × 10⁵), 556 (1.2 × 10⁴), 592 nm (3.5 × 10³).

Disodium 6,6′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}dihexanoate (14)

Salt 14 was prepared from diamide 6 (60 mg, 0.07 mmol) by following the general procedure. The product, which was slightly soluble in H₂O, was washed several times with H₂O and then with Et₂O to give a red solid; yield: 61 mg (99%); mp > 400 °C; R_f  = 0.65 (MeOH–H₂O–Et₃N, 3:1:1).

¹H NMR (500 MHz, TFA-d ₁): δ = 11.26 (s, 1 H, meso), 11.16 (s, 1 H, meso), 11.09 (s, 1 H, meso), 11.07 (s, 1 H, meso), 8.38–8.29 [m, 2 H, –CH= (vinyl)], 6.68 [dd, J = 11.2, 8.3 Hz, 2 H, =CH₂ (vinyl)], 6.47 [dd, J = 17.6, 9.2 Hz, 2 H, =CH₂ (vinyl)], 4.85–4.81 (m, 4 H, por–CH₂–), 3.91 (s, 3 H, por–CH₃), 3.88 (s, 3 H, por–CH₃), 3.85 (s, 3 H, por–CH₃), 3.81 (s, 3 H, por–CH₃), 3.38–3.31 (m, 8 H, –CH₂–, por–CH₂–), 2.47–2.44 (m, 4 H, –CH₂–), 1.71–1.64 (m, 4 H, –CH₂–), 1.62–1.55 (m, 4 H, –CH₂–), 1.37 (br s, 4 H, –CH₂–).

¹³C NMR (125 MHz, TFA-d ₁): δ = 184.0, 178.7, 144.8, 144.7, 144.4, 144.1, 143.5, 143.4, 142.84, 142.80, 142.4, 142.2, 142.0, 141.3, 141.2, 130.5, 130.4, 129.0, 128.9, 103.1, 102.2, 102.0, 100.1, 43.6, 38.2, 38.1 35.1, 29.4, 27.5, 25.6, 24.3, 13.2, 12.6.

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₆H₅₇N₆O₆: 789.4340; found: 789.4329.

UV/Vis (10% HCl in H₂O): λ_max (ε) = 410 (1.62 × 10⁵), 556 (9.44 × 10³), 601 nm (3.59 × 10³).

Disodium (2S,2′S)-2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}bis{6-[(tert-butoxycarbonyl)amino]hexanoate} (15)

Compound 15 was prepared from diamide 7 (50 mg, 0.04 mmol) by following the general procedure. The product was washed successively with H₂O and Et₂O to give a red solid; yield: 49 mg (96%); mp > 400 °C; R_f  = 0.78 (MeOH).

¹H NMR (500 MHz, DMSO-d ₆): δ = 9.97 (s, 1 H, meso), 9.86–9.82 (m, 3 H, meso), 8.49–8.37 [m, 2 H, –CH= (vinyl)], 6.29–6.25 [m, 2 H, =CH₂ (vinyl)], 5.97–5.95 [m, 2 H, =CH₂ (vinyl)], 4.20–4.12 (m, 4 H, por–CH₂–), 3.90 (br s, 2 H, –CH–), 3.65 (m, 6 H, por–CH₃), 3.50–3.48 (m, 6 H, por–CH₃), 3.04 (br s, 4 H, –CH₂ –CONH–), 2.73 (br s, 4 H, –CH₂–), 1.60 (br s, 2 H, –CH₂–), 1.46 (br s, 2 H, –CH₂–), 1.35–1.23 [m, 24 H, –CH₂–, –C(CH₃)₃], 1.15 (br s, 2 H, –CH₂–).

¹³C NMR (125 MHz, TFA-d ₁): δ = 176.7, 176.1, 142.6, 142.3, 142.1, 141.7, 141.5, 141.1, 140.9, 140.0, 139.9, 139.6, 128.3, 128.2, 126.9, 126.8, 125.0, 100.8, 100.0, 99.9, 97.8, 54.4, 52.5, 40.6, 37.0, 29.7, 26.0, 25.8, 21.9, 21.7, 11.0, 10.6.

HRMS-ESI: m/z [M + H]⁺ calcd for C₅₆H₇₅N₁₀O₈: 1019.5600; found: 1019.5635.

UV/Vis (H₂O): λ_max (ε) = 371 (3.25 × 10⁴), 522 (4.54 × 10³), 586 (2.76 × 10³), 640 nm (1.62 × 10³).

Disodium (2S,2′S)-2,2′-{[2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis[(1-oxopropane-3,1-diyl)imino]}bis(6-aminohexanoate) (16)

A cooled 85:10:5 mixture of TFA, CH₂Cl₂, and PhOMe (1.18 mL) was added to a soln of sodium salt 15 (35 mg, 0.03 mmol) in CH₂Cl₂ (0.2 mL), and the mixture was stirred at r.t. for 3 h. Et₂O (20 mL) cooled to 4 °C was added, and the mixture was placed on ice for 5 min to precipitate the product; it was then centrifuged and the crude product was separated and washed with Et₂O (×4) and dried under vacuum overnight to give a red solid; yield: 34 mg (99%); mp > 400 °C; R_f  = 0.38 (MeOH–AcOH–H₂O, 3:1:1).

¹H NMR (500 MHz, TFA-d ₁): δ = 11.03 (s, 1 H, meso), 10.98 (s, 1 H, meso), 10.96 (s, 1 H, meso), 10.94 (s, 1 H, meso), 8.27–8.20 [m, 2 H, –CH= (vinyl)], 6.57 [dd, J = 11.5, 9.0 Hz, 2 H, =CH₂ (vinyl)], 6.35 [dd, J = 17.5, 3.7 Hz, 2 H, =CH₂ (vinyl)] 4.78–4.63 (m, 4 H, por–CH₂–), 4.40–4.33 (m, 2 H, –CH–), 3.81 (s, 3 H, por–CH₃), 3.77 (s, 3 H, por–CH₃), 3.74 (s, 3 H, por–CH₃), 3.70 (s, 3 H, por–CH₃), 3.25–3.16 (m, 2 H, –CH₂ –CONH–), 3.13–3.05 (m, 2 H, –CH₂ –CONH–), 2.99 (br s, 4 H, –CH₂–), 1.65–1.52 (m, 6 H, –CH₂–), 1.40–1.22 (m, 6 H, –CH₂–).

¹³C NMR (125 MHz, TFA-d ₁): δ = 178.8, 178.2, 178.1, 144.7, 144.4, 144.3, 144.2, 143.8, 143.7, 143.4, 143.3, 143.0, 142.2, 142.1, 142.0, 141.8, 141.8, 141.7, 130.4, 130.3, 129.0, 129.0, 102.9, 102.2, 102.0, 99.9, 99.8, 54.6, 42.7, 39.3, 39.2, 31.9, 31.8, 28.0, 24.1, 13.13, 13.12, 12.79, 12.77.

HRMS-ESI: m/z [M + H]⁺ calcd for C₄₆H₅₉N₈O₆: 819.4558; found: 819.4548.

UV/Vis (H₂O): λ_max (ε) = 373 nm (0.2 × 10⁵).

Hexasodium 2,2′-([2,7,12,18-Tetramethyl-3,8-divinylporphyrin-13,17-diyl]bis{(1-oxopropane-3,1-diyl)imino[(2S)-4-oxido-1,4-dioxobutane-2,1-diyl]imino})dipentanedioate (17)

A soln of diamide 8 (30 mg, 0.03 mmol) in CH₂Cl₂ (2 mL) was heated to 40 °C. MeOH (2 mL) followed by 4 M aq NaOH (1 mL) were added, and the mixture was refluxed until the reaction was complete (TLC, ~3 h). Volatile organic products were removed under reduced pressure and the residue was crystallized from H₂O–MeOH and washed several times with MeOH and then with Et₂O to give a red solid; yield: 27 mg (86%); mp > 400 °C; R_f  = 0.9 (MeOH–H₂O–Et₃N, 3:1:1).

¹H NMR (500 MHz, TFA-d ₁): δ = 11.05–11.02 (m, 2 H, meso), 10.96 (s, 2 H, meso), 8.26–8.19 [m, 2 H, –CH= (vinyl)], 6.58–6.54 [m, 2 H, =CH₂ (vinyl)], 6.42–6.36 [m, 2 H, =CH₂ (vinyl)], 4.86–4.56 (m, 8 H, por–CH₂–, CH–), 3.80–3.73 (m, 12 H, por–CH₃), 3.30 (br s, 4 H, –CH₂ –CONH–), 2.74–2.47 (m, 8 H, –CH₂–), 2.25 (br s, 2 H, –CH₂–), 1.98 (br s, 2 H, –CH₂–).

¹³C NMR (125 MHz, TFA-d ₁): δ = 178.8, 175.4, 174.4, 174.3, 172.0, 141.9, 141.73, 141.70, 141.5, 141.4, 141.1, 141.0, 140.6, 140.4, 140.3, 139.8, 139.7, 139.5, 139.3, 139.2, 139.1, 127.7, 127.6, 126.3, 126.2, 124.4, 100.2, 99.3, 99.1, 97.8, 65.5, 53.7, 51.5, 51.4, 48.9, 48.8, 36.2, 35.6, 28.6, 25.0, 21.5, 11.9, 10.4, 10.0.

HRMS-ESI: m/z [M + 7 H – 6 Na]⁺ calcd for C₅₂H₅₉N₈O₁₆: 1051.4053; found: 1051.4049.

UV/Vis (H₂O): λ_max (ε) = 398 (5.37 × 10⁴), 507 (2.94 × 10³), 544 (3.46 × 10³), 566 (2.89 × 10³), 617 nm (1.09 × 10³).

Acknowledgment

This work was supported by the European Regional Development Fund through the TEAM program, grant number TEAM/2009-3/4.

• References

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• References

• 1a Berg JM, Tymoczko JL, Stryer L. Biochemistry . 6th ed. W. H. Freeman; New York: 2007
  Search in Google Scholar
• 1b Schwartz HC, Goudsmit R, Hill RL, Cartwright GE, Wintrobe MM. J. Clin. Invest. 1961; 40: 188
  CrossrefSearch in Google Scholar
• 1c Montforts F.-P, Gerlach B, Höper F. Chem. Rev. 1994; 94: 327
  CrossrefSearch in Google Scholar
• 2a Sibrian-Vazquez M, Hu X, Jensen TJ, Vicente MG. H. J. Porphyrins Phthalocyanines 2012; 16: 603
  CrossrefSearch in Google Scholar
• 2b Evstigneeva RP, Zarubina TV, Zheltukhina GA, Nebol’sin VE, Kaliberda EN, Rumsh LD. Dokl. Chem. (Engl. Transl.) 2001; 381: 349
  CrossrefSearch in Google Scholar
• 2c Sol V, Lamarche F, Enache M, Garcia G, Granet R, Guilloton M, Blais JC, Krausz P. Bioorg. Med. Chem. 2006; 14: 1364
  CrossrefSearch in Google Scholar
• 3a Ignarro LJ, Wood KS, Wolin MS. Proc. Natl. Acad. Sci. U.S.A. 1982; 79: 2870
  CrossrefSearch in Google Scholar
• 3b Wolin MS, Wood KS, Ignarro LJ. J. Biol. Chem. 1982; 257: 13312
  Search in Google Scholar
• 3c Ignarro LJ, Ballot B, Wood KS. J. Biol. Chem. 1984; 259: 6201
  Search in Google Scholar
• 4a Pavlov VYu. Russ. J. Org. Chem. (Engl. Transl.) 2007; 43: 9
  Search in Google Scholar
• 4b Shanmugathasan S, Edwards C, Boyle RW. Tetrahedron 2000; 56: 1025
  CrossrefSearch in Google Scholar
• 4c Razzaque MA, Lord GA, Lim CK. Rapid Commun. Mass Spectrom. 2002; 16: 1675
  CrossrefSearch in Google Scholar
• 4d Giuntini F, Alonso CM. A, Boyle RW. Photochem. Photobiol. Sci. 2011; 10: 759
  CrossrefSearch in Google Scholar
• 5 Doss M, Ulshöfer B. Biochim. Biophys. Acta 1971; 237: 356
  CrossrefSearch in Google Scholar
• 6a Montalbetti CA. G. N, Falque V. Tetrahedron 2005; 61: 10827
  CrossrefSearch in Google Scholar
• 6b Bode JW. Curr. Opin. Drug Discovery Dev. 2006; 9: 765
  Search in Google Scholar
• 7 Matsuo T, Nagai H, Hisaeda Y, Hayashi T. Chem. Commun. (Cambridge) 2006; 3131
• 8 Bhosale SV, Kalyankar MB, Nalage SV, Bhosale SV, Lalander CH, Langford SJ. Supramol. Chem. 2011; 23: 563
  CrossrefSearch in Google Scholar
• 9 Bhosale SV, Bhosale SV, Kalyankar MB, Langford SJ, Lalander CH. Aust. J. Chem. 2010; 63: 1326
  CrossrefSearch in Google Scholar
• 10 Raduhin VA, Philippovich EI, Evstigneeva RP. Zh. Org. Khim. 1979; 50: 673
  Search in Google Scholar
• 11a Molokoedov AS, Philippovich EI, Kazakova NA, Evstigneeva RP. Zh. Org. Khim. 1975; 47: 1165
  Search in Google Scholar
• 11b Pispisa B, Venanzi M, Palleschi A, Zanotti G. Macromolecules 1994; 27: 7800
  CrossrefSearch in Google Scholar
• 11c Traylor TG, Chang CK, Geibel J, Berzinis A, Mincey T, Cannon J. J. Am. Chem. Soc. 1979; 101: 6716
  CrossrefSearch in Google Scholar
• 11d Van der Heijden A, Peer HG, Van der Oord AH. A. Chem. Commun. (Cambridge) 1971; 369
• 11e Pispisa B, Venanzi M, Stella L, Palleschi A, Zanotti G. J. Phys. Chem. B 1999; 103: 8172
  CrossrefSearch in Google Scholar
• 12 Liang G, Wang L, Yang Zh, Koon H, Mak N, Chang CK, Xu B. Chem. Commun. (Cambridge) 2006; 5021
• 13 Nakagawa A, Ohmichi N, Komatsu T, Tsuchida E. Org. Biomol. Chem. 2004; 2: 3108
  CrossrefSearch in Google Scholar
• 14 Gershokvich AA, Kibirev VK. Sintez Peptidov: Reagenty i Metody. Naukova Dumka; Kiev: 1987
  Search in Google Scholar
• 15 Tully DC, Chatterjee AK, Wang Z. WO 2008097676, 2008
• 16 Feichtinger K, Sings HL, Baker TJ, Matthews K, Goodman M. J. Org. Chem. 1998; 63: 8432
  CrossrefSearch in Google Scholar

• Supplementary Material