Synthesis of Pentasaccharide Repeating Unit Corresponding to the Cell Wall O-Polysaccharide of Salmonella enterica O55 Strain Containing a Rare Sugar 3-Acetamido-3-deoxy-d-fucose

Abstract

A pentasaccharide repeating unit corresponding to the cell wall O-antigen of Salmonella enterica O55 containing a rare sugar, 3-acetamido-3-deoxy-d-fucose has been synthesized as its p-methoxyphenyl glycoside using a sequential stereoselective glycosylation strategy. A suitably functionalized 3-azido-3-deoxy-d-fucose thioglycoside derivative was prepared in very good yield and used in the stereoselective glycosylation reaction. Functionalized monosaccharide intermediates were prepared judiciously and stereoselectively assembled to get the desired pentasaccharide derivative in excellent yield.

Total Synthesis and Biological Evaluation of Seiricuprolide and Pestalotioprolide B

“…We decided to convert diol 22 to stannylene acetal by using dibutyltin oxide, followed by employment of PMBCl in the presence of tetrabutylammonium bromide (TBAB) to provide the desired PMB ether 18 in 71 % yield along with 24 % of undesired PMB ether regioisomer. [17] It should be noted that using typical conditions for PMB protection (NaH, PMBCl) or using the more reactive 4-methoxybenzyl 2,2,2trichloroacetimidate [18] gave the undesired PMB ether regioisomer as a major product. Next, m-CPBA epoxidation of allylic alcohol 18 was then performed to give inseparable diastereomeric epoxy alcohols in 78 % combined yield.…”

“…The next task was regioselective protection of primary alcohol of diol 22 with a p ‐metheoxybenzyl (PMB) group. We decided to convert diol 22 to stannylene acetal by using dibutyltin oxide, followed by employment of PMBCl in the presence of tetrabutylammonium bromide (TBAB) to provide the desired PMB ether 18 in 71 % yield along with 24 % of undesired PMB ether regioisomer [17] . It should be noted that using typical conditions for PMB protection (NaH, PMBCl) or using the more reactive 4‐methoxybenzyl 2,2,2‐trichloroacetimidate [18] gave the undesired PMB ether regioisomer as a major product.…”

Ferrier/Aza‐Wacker/Epoxidation/Glycosylation (FAWEG) Sequence to Access 1,2‐Trans 3‐Amino‐3‐deoxyglycosides

“…The yields and selectivities of these methods highly depends on the target [14] . Longer synthesis are also needed when a particular position has to be released for further transformation or glycosylation [3b,15] . The establishment of an efficient reaction sequence giving access to a wide variety of 1,2‐ trans ADGis in few steps would therefore represent a considerable improvement.…”