An alternative approach to the synthesis of anticancer molecule spirobrassinin and its 2′-amino analogues

A convenient synthesis of the cruciferous phytoalexin (S)-(−)-spirobrassinin and its (±)-2′-amino analogues have been achieved. Our synthetic route towards (S)-(−)-spirobrassinin is based on the CrO₃-mediated cyclization of chiral 1-(2′,3′,4′,6′-tetra-O-acetyl-ß-D-glucopyranosyl)brassinin and subsequent removal of the chiral auxiliary. (±)-2′-Amino analogues of spirobrassinin and 1-methoxyspirobrassinin were obtained from thioureas in one step in an efficient manner with the aid of CrO₃. New synthesized compounds were screened in vitro for antiproliferative/cytotoxic activity against six human cancer cell lines by MTT assay. Amino analogues with CF₃ functionality displayed good antiproliferative effect. Graphic abstract: