Rearrangements of the Betulin Core. Synthesis of Terpenoids Possessing the Bicyclo[3.3.1]nonane Fragment by Rearrangement of Lupane-Type Epoxides

Zbigniew Pakulski; Piotr Cmoch; Anna Korda; Roman Luboradzki; Katarzyna Gwardiak; Romuald Karczewski

doi:10.1021/acs.joc.0c02560

Rearrangements of the Betulin Core. Synthesis of Terpenoids Possessing the Bicyclo[3.3.1]nonane Fragment by Rearrangement of Lupane-Type Epoxides

J Org Chem. 2021 Jan 1;86(1):1084-1095. doi: 10.1021/acs.joc.0c02560. Epub 2020 Dec 23.

Authors

Zbigniew Pakulski¹, Piotr Cmoch¹, Anna Korda¹, Roman Luboradzki², Katarzyna Gwardiak¹, Romuald Karczewski¹

Affiliations

¹ Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
² Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.

PMID: 33353300
DOI: 10.1021/acs.joc.0c02560

Abstract

The rearrangements of dihydrobetulin, dihydrobetulinic acid, and abeo-lupane epoxides under acidic conditions (HCl, montmorillonite K10, and BF₃·Et₂O) were studied. The treatment of dihydrobetulin with HCl or K10 produced abeo-lupane olefins. Their epoxidation afforded epoxides, which, in the presence of protic or Lewis acids, rearranged to dienes or lupanes bearing a bicyclo[3.3.1]nonane fragment. The structure of final products depended on the nature of the catalyst. The HCl promoted 1,4-elimination of water, whereas in the presence of BF₃·Et₂O bond migration took place preferentially. Montmorillonite K10 favored cyclization to bicyclononane.

Publication types

Research Support, Non-U.S. Gov't