Methyl pheophorbide-a 1 (700 mg) was dissolved in warm pyridine (10 ml) and the solution was diluted with ether (500 ml). The solution was stirred with a stream of air passing through it, and a solution of KOH (8.0 g) in propanol (20 ml) was added. The bright green mixture was stirred and aerated for 30 min and then extracted with water until the ethereal layer was no longer green. The ethereal solution layer was discarded, the aqueous extracts were combined, adjusted to pH 4 with cone sulfuric acid (8 ml) in water (40 ml), and extracted with dichloromethane until the aqueous layer was no longer green-brown. The combined dichloromethane extract containing unstable chlorin was subjected to repeated evaporation and redissolution in THF (freshly distilled) until no further increase in visible absorption at 700 nm was observed. The product was esterified with ethereal diazomethane and then washed with water, dried and evaporated to dryness. The product was purified by silica column, eluting with 2% methanol in dichloromethane. The appropriate eluates were combined, and the residue obtained evaporating the solvents was crystallized from dichloromethane/methanol to give the title compound in 50% yield (290 mg). m.p. >260° C. (decomp.) (lit., 260-280° C.). max 698 (), 642 (), 592 (), 546 (), 508 (), 478 () and 410 (). NMR ppm 9.55, 9.35, 8.57 (meso H), 7.88 (dd, 11.7, 2-a H), 6.29 (d, 2b-H), 6.18 (d, 2b'H), 5.17 (d, 7-H), 4.38 (q, 8-H), 3.76 (s, 3H), 2.73 (m, 7b-H), 2.47 (m, 7b'H), 2.43 (m, 7a-H), 1.99 (m, 7a'H), 1.74 (d, 8 Me), 1.65 (t, 4b-Me) and 2.01 and -0.09 (each br s, NH); (HRMS 78.2509. C34H34N4O5 requires 578.2529.
