Asymmetric synthesis of (+)-altholactone: a styryllactone isolated from various Goniothalamus species.

The asymmetric total synthesis of (+)-altholactone (1), a member of the styryllactone family of natural products displaying cytotoxic and antitumor activities, is described. Key steps include a RAMP-hydrazone alpha-alkylation (RAMP=(R)-1-amino-2-methoxymethylpyrrolidine) of 2,2-dimethyl-1,3-dioxan-5-one, a boron-mediated aldol reaction, a six- to five-membered ring acetonide shuffling, an oxidative 1,5-diol to delta-lactone conversion and a stereoselective ring-closure to generate the annulated tetrahydrofuran moiety with inversion of configuration.