Stereoselective glycoside synthesis is of interest because of the biological and medical relevance of oligosaccharides, glycoproteins, glycolipids, [1] and other carbohydrate derivatives, [2] and a range of strategies have been developed to produce these compounds. [3] The 1,6-lactone derivative 2 (see Scheme 1) has potential for use in the synthesis of 1,2-cisglycosides [4] but its application has been limited because of the low yields obtained from its reaction with alcohols. [5] We now report that the SnCl 4 -catalyzed coupling of silyl ethers [6] with 2 provides a-O-glucuronides in significantly improved yields without loss of stereoselectivity. The methodology has been extended to the related 2-deoxylactones, which give aor b-glycosides depending on the structure of the donor.
The preparation of 2 was carried out via the mixed anhydride 1 (Scheme 1) by an improved and shorter procedure than that previously described. [5] The donors 6 and 7 were also prepared, via glycal 4, because of their potential for the synthesis of 2-deoxyglycosides, which are of biological interest. [7] Thus, the reaction of the allyl ester 3 with hydrogen bromide in acetic acid gave a glycosyl bromide intermediate [*] Dr.