Diastereoselective Total Syntheses of (±)-Caseabalansin A and (±)-18-Epicaseabalansin A via Intramolecular Robinson-type Annulation

Naoto Okutomi; Akinobu Matsuzawa; Kazuyuki Sugita

doi:10.1002/asia.201900368

Diastereoselective Total Syntheses of (±)-Caseabalansin A and (±)-18-Epicaseabalansin A via Intramolecular Robinson-type Annulation

Chem Asian J. 2019 Jun 14;14(12):2077-2081. doi: 10.1002/asia.201900368. Epub 2019 May 14.

Authors

Naoto Okutomi¹, Akinobu Matsuzawa¹, Kazuyuki Sugita¹

Affiliation

¹ Department of Synthetic Medicinal Chemistry, Faculty of Pharmaceutical Sciences, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo, 142-8501, Japan.

PMID: 30938051
DOI: 10.1002/asia.201900368

Abstract

Highly diastereoselective total syntheses of (±)-caseabalansin A (1) and (±)-18-epicaseabalansin A (2) are described in this paper. We revealed that the intramolecular Robinson-type annulation of an alkynone was effective in the stereocontrolled construction of the bicyclic skeleton of 1 and 2. Further transformation of the resulting enone, including diastereoselective reduction by LiAlH(OtBu)₃ , hydroxy-group-directed hydrogenation, cyclization to form the cyclic acetal moiety, and introduction of a side chain by a C(sp³ )-C(sp³ ) Stille coupling reaction, resulted in the total syntheses of (±)-1 and (±)-2.

Keywords: C-C coupling; annulation; caseabalansin A; natural products; total synthesis.

Abstract

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