Chemical synthesis of a tetrasaccharide related to the exocellular polysaccharide from Rhodococcus sp RHA1

Chemical synthesis of the tetrasaccharide related to the exocellular polysaccharide from Rhodococcus sp. RHA1 is reported. The stereoselective glycosylations were achieved by activation of the thioglycoside donors using N-iodosuccinimide in the presence of La(OTf)(3) varying temperature per the need of 1,2-cis or 1,2-trans glycosylations. The target tetrasaccharide is reported in the form of its p-methoxyphenyl glycoside that can be cleaved selectively from the per-O-acetylated derivative allowing further glycoconjugate formation using trichloroacetimidate chemistry. (C) 2014 Elsevier Ltd. All rights reserved.