SYNTHESIS OF CONJUGATED TRIENES AND RELATED OXIDATION-PRODUCTS OF ALPHA-FARNESENE

The synthesis of conjugated trienes and related oxidation products of alpha-farnesene (1), principally from the epoxides of alpha-farnesene (1), is reported. Base-promoted ring opening of 6,7-epoxide (4) by KOB u(t)/LiNPr2i affords the conjugated triene (2), whilst the 3,4-epoxide (5) affords trienol (7). In contrast, 10,11-epoxide (6) fails to unde rgo epoxide ring opening; it rearranges to the conjugated triene epoxi de (8). Base-promoted ring opening of bisepoxide (9) afforded trienol epoxide (11) at -30 degrees C, whilst cyclization to tetrahydrofurans (10a,b) occurred at room temperature. Photosensitized oxidation of 10, 11-epoxide (6) followed by in situ. treatment with acid gave the cycli c peroxide (3) and on reduction triol (12). Bisallylic alcohol (13) wa s prepared by alkylation of 3-methylsulfolene with geranial. Trienes ( 2) and (3) have been isolated previously as autoxidation products of a lpha-farnesene (1) and are implicated as the causal agents of superfic ial scald of stored apples.