Ascent of De Novo Sugar Synthesis

Initially, the de novo synthesis of enantiomerically pure carbohydrates [110] and glycolipids [111] using transition metal complexes and chiral auxiliaries afforded only modest success. Ultimately, it was the use of enantiomerically pure aldehydes, such as the R and S enantiomers of 2-(phenylseleno)propionaldehyde, to convey facial selectivity upon the LACDAC reaction that enabled the synthesis of optically pure glycals. Syntheses of several complex monosaccharides such as the main sialic acid-type N-acetylneuraminic acid (Neu5Ac) and rac-3-deoxy-ma o-2-octulosonic acid (KDO) were accomplished with this technology [112, 113], The LACDAC 

SCHEME 1.4 Enantioselective synthesis of L-glucose via the LACDAC reaction, hfc, 3-(heptafluoropropylhydroxymethylene)-D-camphorato TBS, ferf-butyldimethylsilyl. 

SCHEME 1.5 LACDAC reaction in the total synthesis of Neu5Ac. Bz, benzoyl TMS, trimethylsilyl. 

SCHEME 1.6 General scheme for a reagent-controlled approach to the total synthesis of all eight L-hexoses. 

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