Asymmetric total synthesis of terpenoids possessing novel structure or biological activity

Abstract

Asymmetric total synthesis of sarcophytols A and T, hippospongic acid A, octalactin A and glabrescol has been summarized in this review. Baker's yeast reduction is used as a chilarity induction method. Both enantiomers of sarcophytols A and T, an inhibitor of tumor promoter, were synthesized using stereospecific [2,3]-Wittig rearrangement as the key step. The structure of hippospongic acid A exhibiting inhibitory activity for gastrulation of starfish embryos was revised by asymmetric synthesis and its absolute configuration was determined. A key compound for the synthesis of cytotoxic octalactin A was prepared efficiently starting from (-)-citronellol. A compound having the structure proposed for glabrescol, a meso-type triterpene containing five continuously linked tetrahydrofuran rings, and one of its diastereomer were synthesized enantio-selectively. Comparison of NMR spectra of all of thus synthesized authentic diastereomers revealed that there was some mistakes in elucidation of the stereochemistry of the natural product.