Issue 12, 2016

Configuration-guided reactions: the case of highly decorated spiro[cyclopropane-1,2′(3′H)-pyrrolo[1,2-b]isoxazole] derivatives en route to polyhydroxyindolizidines

Abstract

In the course of studies directed toward the synthesis of 7,8-disubstituted 1,2-dihydroxyindolizidines as analogues of the proapoptotic iminosugar lentiginosine, marked reactivity differences of diastereomeric spiro[cyclopropane-1,2′(3H)-pyrrolo[1,2-b]isoxazolidines] precursors were observed. While one minor diastereoisomer gives the Brandi–Guarna rearrangement to indolizidinone very smoothly, and also easily undergoes fluorination of the primary alcohol, the main diastereoisomer behaves in a rather different way. The thermal rearrangement is less efficient and fluorinating agents mainly induce an unexpected cyclization to a highly strained tetracyclic derivative that, in turn, rearranges to form the uncommon 2-oxa-8-azatricyclo[6.2.1.04,9]undecan-5-one system with good yield. In this last process a remarkable macrocyclic dimer has been isolated that sheds light on an unprecedented different aspect of the Brandi–Guarna rearrangement.

Graphical abstract: Configuration-guided reactions: the case of highly decorated spiro[cyclopropane-1,2′(3′H)-pyrrolo[1,2-b]isoxazole] derivatives en route to polyhydroxyindolizidines

Supplementary files

Article information

Article type
Research Article
Submitted
29 jul. 2016
Accepted
12 sep. 2016
First published
13 sep. 2016

Org. Chem. Front., 2016,3, 1651-1660

Configuration-guided reactions: the case of highly decorated spiro[cyclopropane-1,2′(3′H)-pyrrolo[1,2-b]isoxazole] derivatives en route to polyhydroxyindolizidines

F. M. Cordero, C. Vurchio, C. Faggi and A. Brandi, Org. Chem. Front., 2016, 3, 1651 DOI: 10.1039/C6QO00410E

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