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Paper | Special issue | Vol 39, No. 1, 1994, pp.81-100
Published online, 1st January, 1970
DOI: 10.3987/COM-93-S(B)2
The Dolastatins 16. Synthesis of Dolaphenine

George R. Pettit,* Fiona Hogan, Douglas D. Burkett, Sheo B. Singh, Darko Kantoci, Jayaram Srirangam, and Michael D. Williams

*Cancer Research Institute, Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

Abstract

Synthesis of dolaphenine (2), the thiazole-containing unit of the strongly antineoplastic peptide dolastatin 10 (1), has been summarized. While conversion (47 or 411) of phenylalanine to thiazolidines (7) or thiazolines (11) was routinely uneventful, a dependable procedure for dehydrogenation of these intermediates to dolaphenine (2, Doe) proved elusive. While several types of specially prepared manganese dioxide were found most effective for the dehydrogenation, yields of dolaphenine varied from almost nil to over 70%. Some of these reactions resulted in partial to complete racemization of the phenylalanine derived chiral carbon.