Studies on the Enantioselective Synthesis of E-Ethylidene-bearing Spiro[indolizidine-1,3'-oxindole] Alkaloids.

ABSTRACT: A synthetic route for the enantioselective construction of the tetracyclic spiro[indolizidine-1,3'-oxindole] framework present in a large number of oxindole alkaloids, with a cis H-3/H-15 stereochemistry, a functionalized two-carbon substituent at C-15, and an E-ethylidene substituent at C-20, is reported. The key steps of the synthesis are the generation of the tetracyclic spirooxindole ring system by stereoselective spirocyclization from a tryptophanol-derived oxazolopiperidone lactam, the removal of the hydroxymethyl group, and the stereoselective introduction of the E-ethylidene substituent by acetylation at the ?-position of the lactam carbonyl, followed by hydride reduction and elimination. Following this route, the 21-oxo derivative of the enantiomer of the alkaloid 7(S)-geissoschizol oxindole has been prepared.

SUBMITTER: Yayik N 

PROVIDER: S-EPMC7829768 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature