@article {3754,
	title = {Stereoselective synthesis of new chlorophyll A related antioxidants isolated from marine organisms},
	journal = {Journal of Organic Chemistry},
	volume = {61},
	number = {7},
	year = {1996},
	note = {ISI Document Delivery No.: UD653Times Cited: 39Cited Reference Count: 37},
	month = {Apr},
	pages = {2501-2510},
	type = {Article},
	abstract = {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.},
	keywords = {2-SULFONYLOXAZIRIDINES, CHEMISTRY, COMPOUND, DERIVATIVES, enol, HYDROXYLATION, ORIGINS, RCI, RUDITAPES-PHILIPPINARUM},
	isbn = {0022-3263},
	url = {<Go to ISI>://A1996UD65300039},
	author = {Ma, L. F. and Dolphin, D.}
}
