Issue 2, 2018

Beyond optical rotation: what's left is not always right in total synthesis

Abstract

This work describes the application of vibrational (VCD) and electronic (ECD) circular dichroism spectroscopy to solve the longstanding debate around the absolute configuration of (+)-frondosin B (1). The absolute configuration of (+)-1 could confidently be assigned as (R) using these spectroscopic techniques. The discrepancy in the optical rotation (OR) values obtained in previous studies can be attributed to an undetected minor impurity (ca. 7%) that arose unexpectedly in a key step late in the synthesis. Additionally, the conditions used in the final step of the previous reports for demethylation to form the natural product proceeded with significant loss of enantiopurity. The large OR measured for the impurity at its observed level, when compared to the small rotation for the less enantiopure natural product 1, led to a measured OR value for the synthetic material that had the opposite sign of the natural product.

Graphical abstract: Beyond optical rotation: what's left is not always right in total synthesis

Supplementary files

Article information

Article type
Edge Article
Submitted
28 Sep 2017
Accepted
27 Oct 2017
First published
30 Oct 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2018,9, 415-424

Beyond optical rotation: what's left is not always right in total synthesis

L. A. Joyce, C. C. Nawrat, E. C. Sherer, M. Biba, A. Brunskill, G. E. Martin, R. D. Cohen and I. W. Davies, Chem. Sci., 2018, 9, 415 DOI: 10.1039/C7SC04249C

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