Synthesis 2016; 48(19): 3339-3351
DOI: 10.1055/s-0035-1562500
paper
© Georg Thieme Verlag Stuttgart · New York

Stereoselective Ethynylation and Propargylation of Chiral Cyclic Nitrones: Application to the Synthesis of Glycomimetics

Sara García-Viñualesa, Ignacio Delsoa, b, Pedro Merinoa, Tomás Tejero*a
  • aLaboratorio de Síntesis Asimétrica, Departamento de Síntesis y Estructura de Biomoléculas, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), Universidad de Zaragoza, CSIC, Campus San Francisco, 50009 Zaragoza, Aragón, Spain   Email: ttejero@unizar.es
  • bServicio de NMR, Centro de Química y Materiales de Aragón (CEQMA), Universidad de Zaragoza, CSIC, Campus San Francisco, 50009 Zaragoza, Aragón, Spain
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Publication History

Received: 13 May 2016

Accepted after revision: 02 June 2016

Publication Date:
11 July 2016 (eFirst)

Dedicated to Prof. J. Normant on occasion of his 80th birthday. Sadly, Prof. J. Normant passed away June 9.

Abstract

Ethynylation and propargylation of chiral nonracemic polyhydroxylated cyclic nitrones with Grignard reagents are efficient methods for preparing building blocks containing an alkyne moiety to be used in copper-catalyzed azide alkyne cycloaddition click chemistry. Whereas ethynylation takes place with excellent diastereoselectivity, propargylation afforded mixtures of diastereomers in some cases. The use of (trimethylsilyl)propargyl bromide as precursor of the Grignard reagent is necessary to avoid the formation of undesired allene derivatives. DFT calculations explain, within the experimental error, the observed behavior. Cycloaddition of the obtained pyrrolidinyl alkynes with sugar azides derived from β-(1,3)-glucans provides glycomimetics suitable to be used against fungal transglycosylases.

Supporting Information