Studies on Total Synthesis of the Olivomycins

Studies directed toward total synthesis of olivin (4), the aglycon of the olivomycin antitumor antibiotics, are described. The key aldehyde 23, containing the tricyclic nucleus of olivin, has been prepared in 14 steps from 3,5-di-methoxybenzyl chloride. Methods for construction of the olivin hydroxy ketone side chain were also investigated. Attempted addition of trianion 24 to simple aldehydes was unsuccessful. Cyclohexanecarboxaldehyde, a model for aldehyde 23, was converted to dithiane 36, which in two steps was transformed to ketone 38. Hydroxylation of 38 with m-CPBA via a kinetic enolate and trimethylsilyl ether 39 produced a single acyloin, having either structure 40 or 42.