A NEW ENANTIOSPECIFIC SYNTHESIS OF ALPHA-SANTALANES VIA HOMOFRAGMENTATION OF 1,4-DIOL MONOSULFONATE ESTERS

The homofragmentation of 1,4-diol monosulfonate esters was applied as a key step in the synthesis of alpha-santalanes. The enantiospecific s ynthesis of (+)-alpha-santalan-12-one (Id) was achieved via the tricyc lic dione 2 as an intermediate that could be obtained from (R)-(-)-car vone. A 1,2-carbonyl transposition in dione 2 followed by functional g roup transformations afforded the tricyclic 1,4-diol monomesylate 3, w hich could be homofragmented in 76% yield to the tricyclic aldehyde 4. From this compound the synthesis of several alpha-santalanes can be a chieved; the synthesis of Id was accomplished in 11 steps from 2 in 8% overall yield.