Terpenoids-CXIII: synthesis of α-santalene, α-santalol, α-santalic acid and allied products

Abstract

Earlier findings in the santalene-santalol series have been re-examined and extended. Tricycloekasantalic acid VI, the corresponding alcohol VIII, the aldehyde XIII and homotricycloekasantalic acid XI have been synthesized starting from V. The reaction of the methyl ester of XI with methyl magnesium iodide yields the crystalline alcohol, 13-hydroxy-α-santalene (X) dehydration of which affords a mixture of a-santalene (III) and the isomeric hydrocarbon XII, from which pure III is separated (TLC). The Wittig reagent prepared from ethyl-a-bromopropionate reacts with the aldehyde XIII to yield pure, crystalline α-santalic acid (XVI) the ethyl ester of which on reduction with LAH is converted to α-santalol (I),IR, UV and NMR spectral data are consistent with the structures.