ChemInform Abstract: Asymmetric Conjugate Additions of an Hydroxyethyl Carbanion Equivalent. Synthesis of (+)-A Factor.

ChemInform Abstract

The chiral tolylsulfinylbutenolide (S)-(+)-(IV) is coupled with the lithiated bisether which is prepared from benzyloxymethyl chloride (I) and the hydroxymethylstannane (II) by lithium tin exchange. The crude product is directly desulfurized with Raney nickel, yielding the alkylated γ-lactone (+)-(V). This is acylated with isooctanoyl chloride (VI), producing the keto lactone (VII). Deprotection is achieved by catalytic hydrogenation to give (+)-A factor (VIII) which is an autoregulative for the production of streptomycin.