Stereocontrolled synthesis of (3Z,5E)-6-aryl-3-methylhexa-3,5-dien-1-ols, intermediates in the synthesis of strobilurin antibiotics

Abstract

2E,4E) 5 Aryl 2 (2 benzyloxyethyl)penta 2,4 dien 1 als (aryl is phenyl and 4 methox yphenyl) were reduced with NaBH 4 quantitatively and stereospecifically to the corresponding penta 2(E),4(E) dien 1 ols. The hydroxymethyl group in the latter was transformed into a methyl one with a stereoselectivity of 92-97%. Debenzylation of the resulting (1E,3Z) 1 aryl 6 benzyloxy 4 methylhexa 1,3 dienes with AlCl 3 in the presence of PhNMe 2 afforded the target (3Z,5E) 6 aryl 3 methylhexa 3,5 dien 1 ols; the configuration of the C=C bonds in the con jugated aryl diene systems was retained at 95%.