Issue 3, 2006

Practical formal total synthesis of (rac)- and (S)-camptothecin

Abstract

A practical, efficient and scalable formal total synthesis of (rac)- and (S)-camptothecin is described, which proceeds via the known DE ring building blocks 19 and (S)-19, respectively. The racemic synthesis starts from diethyl oxalate and uses straightforward carbonyl chemistry in order to generate the pyridone ring system. 19 was formed in 8.4% overall yield over 9 linear steps avoiding any chromatographic purification. The asymmetric version of this approach encompassed a diastereoselective Grignard addition to the enantiomerically pure α-ketoester 30 in order to generate the (S)-configured quaternary stereocenter. The auxiliary could be recycled in high yield and was successfully reused multiple times. The final steps paralleled the racemic approach. (S)-19 was thus prepared in 9.4% overall yield (er = 95 : 5) over 10 steps.

Graphical abstract: Practical formal total synthesis of (rac)- and (S)-camptothecin

Article information

Article type
Paper
Submitted
10 Oct 2005
Accepted
21 Nov 2005
First published
22 Dec 2005

Org. Biomol. Chem., 2006,4, 498-509

Practical formal total synthesis of (rac)- and (S)-camptothecin

R. Peters, M. Althaus and A. Nagy, Org. Biomol. Chem., 2006, 4, 498 DOI: 10.1039/B514147H

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