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Synlett 2010(1): 142-144  
DOI: 10.1055/s-0029-1218540
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

The Structure and Stereochemistry of Gabosine K: Syntheses of 7-O-Acetylstreptol and 7-O-Acetyl-1-epi-streptol

Tony K. M. Shing*, Hau M. Cheng
Department of Chemistry and Center of Novel Functional Molecules, The Chinese University of Hong Kong, Shatin, Hong Kong, P. R. of China
Fax: +85226035057; e-Mail: tonyshing@cuhk.edu.hk;
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Publication History

Received 18 September 2009
Publication Date:
02 December 2009 (online)

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Abstract

Gabosine K, whose structure was erroneously assigned previously as 7-O-acetyl-4-epi-streptol, has been synthesized for the first time from d-glucose via a key carbocyclization strategy, intramolecular direct aldol reaction of a 2,6-diketone, in 15 steps with 13.5% overall yield. In the same manner, (+)-7-O-acetyl-streptol has been constructed for NMR spectral comparison. The structure, relative and absolute configurations of (-)-gabosine K are now revised and established as (-)-7-O-acetyl-1-epi-streptol, that is, (1R,2S,3S,4R)-tetrahydroxy-5-acetoxymethylcyclohex-5-ene. Since the specific rotation of the natural product is not available, the absolute configuration of natural gabosine K is either (-)-7-O-acetyl-1-epi-streptol or its enantiomer.

Key words

carbasugars - carbohydrates - stereoselective synthesis - aldol reactions - natural products

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