Synthesis of Three Acyclic All-trans-Tetraterpene Diols, Putative Precursors of Bacterial Lipids

Three acyclic all-trans-tetraterpene diols, A, B, and C have been synthesized from geraniol (1), by a convergent scheme involving six different C10 synthons derived from geraniol, and coupling by known reactions of three different types: substitution of allylic chlorides by carbanions α to sulfones, duplication of allylic alcohols, and Pd(0)-catalyzed coupling of allylic carbonates with doubly stabilized carbanions. A, B, and C represent postulated phylogenetic precursors of known membrane reinforcers, and are the three possible distally dihydroxylated dimers of geranylgeraniol: tail-to-tail, head-to-head, and head-to-tail.