Further Investigation of the 2‐Azido‐phenylselenylation of Glycals

Abstract Derivatives of 2‐azido‐2‐deoxysugars are widely applied as precursor of 2‐amino‐2‐deoxysugars in the synthesis of various oligosaccharides of bacterial, fungal and mammalian origin. Heterogeneous or homogeneous azidophenylselenylation (APS) of glycals, i. e., reaction of glycals with Ph 2 Se 2 , PhI(OAc) 2 and NaN 3 or TMSN 3 as azide radical donors, is a straightforward way to phenyl 2‐azido‐2‐deoxy‐1‐selenoglycosides that can be directly used as glycosyl donors. However, heterogeneous APS is characterized by insufficient reproducibility and scalability. We have studied the effect of reaction conditions on the product distribution in heterogeneous APS of 3,4,6‐tri‐ O ‐acetyl‐ d ‐galactal and found the conditions that enabled reliable preparation of crystalline phenyl 2‐azido‐2‐deoxy‐1‐seleno‐α‐ d ‐galactopyranoside triacetate in yield of 58 % on the 3.7 mmol scale. APS of 3,4,6‐tri‐ O ‐acetyl‐ d ‐glucal under those conditions produced a ∼1 : 1 mixture of phenyl 2‐azido‐2‐deoxy‐1‐seleno‐α‐ d ‐gluco‐ and mannopyranosides in total yield of 78 %. Acetoxyphenylselenylation of differently protected galactals and 3,4,6‐tri‐ O ‐acetyl‐ d ‐glucal under the action of Ph 2 Se 2 and PhI(OAc) 2 has been shown to be a convenient method for the synthesis of 1‐ O ‐acetyl‐2‐seleno‐2‐deoxy derivatives, valuable intermediates in chemistry of 2‐deoxysugars. 2‐Seleno‐2‐deoxy sugars were characterized in detail by NMR data including 77 Se chemical shifts and n J Se−H coupling constant values.