Seongkon Kim

Chromium [II]-mediated reductive cleavage of a tertiary halide bearing three β-alkoxy groups. Synthesis of the north hexacyclic steroid unit of the cephalostatin family

Transformation of aldehyde 4 to 17nat, a hexacyclic steroid bearing the requisite functionality and spiroketal stereochemistry of the North portion of the cephalostatin family is described. The key reaction involves CrCl2 mediated reductive cleavage of a tertiary bromide which is beta to three alkoxy groups.

Application of the Reich iodoso syn-elimination for the preparation of an intermediate appropriate for the synthesis of both hexacyclic steroidal units of cephalostatin 7☆

Abstract Hecogenin acetate 5 was converted to an intermediate suitable for construction of both “North” and “South” hexacyclic spiroketals present in cephalostatin 7. The key chemical transformations involved are: (1) the Reich iodoso syn-elimination of iodide 18; (2) Rhodium [II] catalyzed intermolecular oxygen alkylation of secondary neopentyl alcohol 21; and (3) Intramolecular Wadsworth-Emmons reaction to provide the ester precursor of aldehyde 4.