Glycals nitrosyl chloride addition

The cis addition of nitrosyl chloride to substituted cyclic enol ethers and O-protected glycals, rationalized as either molecular addition through a four-centered polar transition state or by radical mechanism, generally takes place with complete simple and induced diastereose-lectivity45-47. 

The azidonitration route to 2-amino-2-deoxy sugars from D-glycal should be compared with the alternative route exploiting the addition of nitrosyl chloride (Section 7.2.1.1). Both methods have been tested on the synthesis of intermediates of D-lactosamine, and the azidonitration method was considered more efficient95. 

Products of considerable potential interest for the synthesis of 2-amino-2-deoxyaldose derivatives have been obtained by the addition of nitrosyl chloride to acetylated glycals. Tri-O-acetyl-n-glucal and di-O-acetyl-n-arabinal react smoothly in carbon tetrachloride at 0° to give crystalline products which, on the basis of their chemical reactivities and their nuclear magnetic resonance spectra, have been assigned the structures of tri-0-acetyl-2-deoxy-2-nitroso-Q -D-glucopyranosyl chloride (32) and di-O-acetyl-2-deoxy-2-nitroso-j3-n-arabinopyranosyl chloride (33). It was not estab-... 

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