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Synlett 2012; 23(18): 2687-2691
DOI: 10.1055/s-0032-1317382
letter
© Georg Thieme Verlag Stuttgart · New York

One-Pot Enantioselective Synthesis of Tryptophan Derivatives via Phase-Transfer Catalytic Alkylation of Glycine Using a Cinchona-Derived Catalyst

Robert Todd
Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 N. Cramer Street, Milwaukee, WI 53211-3029, USA   Fax: +1(920)2295530   Email: mahmun@uwm.edu
,
Matthew Huisman
Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 N. Cramer Street, Milwaukee, WI 53211-3029, USA   Fax: +1(920)2295530   Email: mahmun@uwm.edu
,
Nazim Uddin
Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 N. Cramer Street, Milwaukee, WI 53211-3029, USA   Fax: +1(920)2295530   Email: mahmun@uwm.edu
,
Sarah Oehm
Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 N. Cramer Street, Milwaukee, WI 53211-3029, USA   Fax: +1(920)2295530   Email: mahmun@uwm.edu
,
M. Mahmun Hossain*
Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 N. Cramer Street, Milwaukee, WI 53211-3029, USA   Fax: +1(920)2295530   Email: mahmun@uwm.edu
› Author Affiliations
Further Information

Publication History

Received: 12 July 2012

Accepted after revision: 18 September 2012

Publication Date:
18 October 2012 (online)

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Abstract

Tryptophans are building blocks for many natural products. This paper describes the enantiospecific synthesis of ring-A substituted tryptophan derivatives from commercially available gramines using chiral phase-transfer conditions. This one-pot reaction avoids protecting/deprotecting the indolylic nitrogen of gramine by choosing a chemoselective quaternization reagent, 4-(trifluoro-methoxy)benzyl bromide, to produce an electrophilic salt intermediate, which is subsequently alkylated in good yield with high enantiomeric excess.

Key words

asymmetric synthesis - one-pot - organocatalysis - phase transfer - tryptophan

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  • References and Notes

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