Synthesis of 3-Pyrazolinyl Chlorins Related to Chlorophyll by 1,3-Dipolar Cycloaddition Reaction from Methyl Pheophorbide-<i>a</i>
作者:Jin-Jun Wang、Chun-Lin Liu、Jia-Zhu Li
DOI:10.1080/00397911.2010.525776
日期:2012.2.15
Abstract The synthesis of a series of 3-pyrazolinyl-substituted chlorins, possessing different basic skeletons of chlorophyll degradation products such as pheophorbide-a, pyropheophorbide-a, purpurin-18, purpurin-7, purpurin-5, chlorin-p 6, and chlorin-e 6, was fulfilled from methyl pheophorbide-a by chemical modification and 1,3-dipolarcycloaddition with diazomethane. The structures of new chlorins
Stereoselective Synthesis of New Chlorophyll <i>a</i> Related Antioxidants Isolated from Marine Organisms
作者:Lifu Ma、David Dolphin
DOI:10.1021/jo951854i
日期:1996.1.1
A new class of natural antioxidants, chlorophyll a related chlorins 3, 4(S), 4(R), 5(R), 6, 7, 8, and 9, have been synthesized from a chlorophyll a degradation product, pheophorbide a methyl ester (1). Claisen-type intramolecular condensation of pyropheophorbide a methyl ester (2) afforded the common intermediate enol 3. Chlorin 1 and enol 3 have a propensity to undergo exocyclic ring opening by ionic bases. The organic base DBU was found to be an efficient reagent for promoting the asymmetric hydroxylation of these chlorins, using N-sulfonyloxaziridines, without cleavage of the exocyclic rings. Model studies for hydroxylactonization have shown that periodate oxidation of hydroxy ketone 10 stereoselectively and predominantly forms hydroxy lactone 17(S). Periodate oxidation of alpha-hydroxy 1,3-diketone 4(R) and/or 4(S) to furnish hydroxy lactone 5(R) and diketone 7 was found out to be regioselective, and the site of reaction depends on the appropriate choice of reaction media. H-1 NMR spectra have provided information on the absolute configuration of diastereomers at the C-13(2) or C-15(1) position.
Fischer; Lautsch, Justus Liebigs Annalen der Chemie, 1937, vol. 528, p. 265,274