POLYENE SYNTHESIS - READY CONSTRUCTION OF RETINOL CAROTENE FRAGMENTS, (+/-)-6(E)-LTB3 LEUKOTRIENES, AND CORTICROCIN

All products of the dirhodium tetraacetate catalyzed reactions of ethyl diazoacetate with furan, 2-methylfuran, 2,5-dimethylfuran, 2-n-octylfuran, methyl furoate and methyl β-(α-furyl) acrylate were isolated and characterized. They consist mostly of exo-cyclopropanecarboxylates and 1,4-diacyl-1,3-butadienes and some 3-(acylmethyl)furans. Treatment of the crude reaction mixtures with iodine or boron trifluoride furnishes 1,4-diacyl-1(E),3 (E)-butadienes. Horner-Emmons condensation with the latter dicarbonyl compounds leads to 1,6-diacyl-1,3,5-hexatrienes. Proper combinations of methyl a-diazopropionate, furans, and a-phosphono esters afford segments of retinol and 0-carotene, while combinations of a-diazo ketones, furans, and a-phosphono ketones yield LTB3-like leukotrienes. Finally, dirhodium tetraacetate promoted decomposition of ethyl diazoacetate in l,2-bis(2-furyl)ethane and iodine treatment gives a diketo diester, whose reduction, dehydration, and hydrolysis leads to the naturally occurring dodecahexaenic dicarboxylic acid, corticrocin. © 1990, American Chemical Society. All rights reserved.