Syntheses of deuterated methyl 9,15‐octadecadienoate and methyl 9,12,15‐octadecatrienoate geometric isomers

Abstract

AbstractMethyl 9,15‐octadecadienoate‐6,7‐d2 isomers (12) were obtained by Wittig coupling between methyl 9‐oxononanoate‐6,7‐d2 (6) and 6‐nonenyltriphenylphosphonium bromide (11). Compound 11 was prepared from methyl 6‐nonenoate (8) by reduction‐With sodium bis(2‐methoxyethoxy)aluminum‐hydride, bromination with triphenylphosphine dibromide and further reaction with triphenylphosphine. Synthesis of compound 8 was achieved by Wittig coupling between propyltriphenylphosphonium bromide (7) and methyl 6‐oxohexanoate (1) which was obtained by ozonolysis of cyclohexene. Compound 6 was prepared through the dimethoxy derivative from methyl 8‐dioxanyloctanoate‐6,7‐d2 (4) which was obtained by deuteration of methyl 8‐dioxanyloctanoate‐6,7‐d2(4) which was obtained by deuteration of methyl 8‐dloxanyl‐6‐octenoate (3) with tris(triphenylphosphine)chlororhodium and deuterium gas. Compound 3 was obtained from compound 1 by chain extension with [2‐(1,3‐dioxan‐2‐yl)ethyl]triphenylphosphonium bromide (2). Chain extension of 6 with 2 yielded methyl 11‐dioxanyl‐9‐undecenoate‐6,7‐d2(13). The latter was converted to methyl 12‐oxo‐9‐dodecenoate‐6,7‐d2 (15) which was treated with 3‐hexenyltriphenylphosphonium bromide (16) and butyl lithium to give methyl 9,12,15‐octadecatrienoate isomers (17). Geometric isomers formed during each of the Wittig reactions were separated by silver resin chromatography.