Unusual Epimerization in Styryllactones: Synthesis of (-)-5-Hydroxygoniothalamin, (-)-5-Acetylgoniothalamin, and O-TBS-Goniopypyrone

Tharun K Kotammagari; Sayantan Paul; Asish K Bhattacharya

doi:10.1021/acsomega.9b03263

Unusual Epimerization in Styryllactones: Synthesis of (-)-5-Hydroxygoniothalamin, (-)-5-Acetylgoniothalamin, and O-TBS-Goniopypyrone

ACS Omega. 2019 Dec 17;4(27):22549-22556. doi: 10.1021/acsomega.9b03263. eCollection 2019 Dec 31.

Authors

Tharun K Kotammagari¹, Sayantan Paul¹, Asish K Bhattacharya¹

Affiliation

¹ Division of Organic Chemistry and Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India.

Abstract

(-)-5-Hydroxygoniothalamin, (-)-5-acetylgoniothalamin, and (+)-5-hydroxygoniothalamin, isolated from the Goniothalamus genus, are synthesized from triacetyl-O-d-glucal by employing the Ferrier reaction, Mitsunobu reaction, and Jones oxidation as key steps. The synthetic procedure also yields the epimers of (-)-5-hydroxygoniothalamin and (+)-5-hydroxygoniothalamin employing acid-mediated transition-metal-free epimerization at C-5 of styryllactones. Further studies reveal that the epimerization is facilitated by the phenyl group present on the styryllactones. Also, depending on the dihydroxylation reaction conditions, various analogues of saturated styryllactones are synthesized utilizing oxa-Michael reaction conditions.