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The Total Synthesis of Allosamidin. Expansions of the Methodology of Azaglycosylation Pursuant to the Total Synthesis of Allosamidin. A Surprising Enantiotopic Sense for a Lipase-Induced Deacetylation

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journal contribution
posted on 09.10.1996, 00:00 by David A. Griffith, Samuel J. Danishefsky
Allosamidin, recently isolated from mycelial extracts of Streptomyces sp. 1713, is a powerful and selective chitinase inhibitor. The total synthesis of allosamidin is described herein. The electric eel acetylcholinesterase-mediated enantioselective hydrolysis of (trans,trans)-2-(benzyloxy)cyclopentene-1,3-diol diacetate accessed a monoacetyl derivative. Five additional steps produced a protected version of the aglycon (“allosamizoline”) sector of allosamidin. An allal derivative stereoselectively reacted with benzenesulfonamide in the presence of a halonium source to afford a 2β-halo-1α-sulfonamidohexose. Treatment of this product with a strong base generated an intermediate 1,2-sulfonylaziridine, which was trapped with a protected allal derivative to provide a disaccharide glycal. Reiteration of this scheme gave access to the required trisaccharide. Following deprotection, the total synthesis of allosamidin was accomplished. In addition, the method, with modification, gave access to several allosamidin analogs.