Monosaccharide Isocyanides Employed in the Ugi and Passerini Reaction

The synthesis works best with benzylated halogeno sugars 390 and provides a mixture of anomeric (a + p) isocyanides 391. The isocyanides can also be synthesized by desulfurization of glycosyl isothiocyanates [128]. 

The Ugi reactions were carried out using i-butanal as the aldehyde component and N-Boc-glycine and IV-propyl amine or (5)-serine in methanol. The reactions again proceeded with low diastereoselectivity and also a low yield. 

SCHEME 7.120 Products of Passerini and Ugi reactions of glycosyl isocyanides. 

The Ugi reactions, however, did not show any considerable differences between the anomeric glucosyl isocyanides and 2-isocyanoglucose. No higher reactivity was observed. Reactions times were still slow and yields continued to be low. 

Although the reaction conditions did not yield optimal results, Ziegler did show that it was possible to achieve complex glycopeptide derivatives using anomeric glycosyl isocyanides or isocyanoglucoses. 

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