W-Acetyl-D-mannosamine

Scheme 11 Possible intermediates involved in the reaction of Af-acetyl-D-glucosamine (66) and W-acetyl-D-mannosamine (67)...

Having set up a protocol for the aminohomologation of various aldehydo sugars, the value of the method was tested by the synthesis of simple natural products. The firsl example involved [57a] the conversion of 2,3 4,5-di-0-isopropylidene-D-arabinose 59 (Scheme 18) through the nitrone 60 into the W-acetyl-D-mannosamine diacetonide 61 and the deprotected compound 11, both well-known key intermediates for the synthesis of /V-acetylneuraminic acid (Neu5Ac) [59,60]. Unfortunately, in this case the addition of 2-LTT (25b) to the nitrone 60 occurred with modest selectivity (ds 75% to the best) therefore, the overall yield of 61 was quite low (29%). 

The reversed configuration of these adducts that was mistakenly assigned in our first report (Ref 57a) was timely corrected in a second paper (Ref 57b). For a commentary to this reaction, see A. Zamojski, Stereoselective aminohomologation of chiral a-alkoxy aldehydes via thiazole addition to nitrones. Application to the synthesis of W-acetyl-D-mannosamine, Chemtracts Org. Chem. 6 172 368 (1993). 

Scheme 11.—Chemical Synthesis of Differently Substituted W-Acetyl-D-mannosamine Derivatives.

Carroll, P. M., and Comforth, J. W., 1960, Preparation of N-acetylneuraminic acid from A-acetyl-D-mannosamine, Biochim. Biophys. Acta 39 161. 

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