A tetrasaccharide repeating unit corresponding to the cell-wall lipopolysaccharide of E. coli O40 was synthesized by using a convergent block glycosylation strategy. A disaccharide donor was coupled to a disaccharide acceptor by a stereoselective glycosylation. A 2-aminoethyl linker was chosen as the anomeric protecting group at the reducing end of the tetrasaccharide. All glycosylation steps are significantly high yielding and stereoselective.
Numerous O (oxa)- and S (thia)-glycosyl esters and their analogous glycosyl
acids have been accomplished through stereoselective glycosylation of various peracetylated
bromo sugar with benzyl glycolate using InBr3 as a glycosyl promotor followed
by in situ hydrogenolysis of resulting glycosyl ester. A tandem glycosylating and hydrogenolytic
activity of InBr3 has been successfully investigated in a one-pot procedure. The
resulting synthetically valuable and virtually unexplored class of β-CMGL (glycosyl acids)
could serve as an excellent potential chiral auxiliary in the asymmetric synthesis of a
wide range of enantiomerically pure medicinally prevalent β-lactams and other bioactive
molecules of diverse medicinal interest.
AbstractA convergent synthesis of IMMH002 in 36% overall yield starting from bromobenzene is described with a key Suzuki–Miyaura cross-coupling reaction used to provide a crucial intermediate. The route does not require column chromatography and solves the most intractable quality problem caused by a homologue by-product in the original linear synthesis. Furthermore, reducing the use of Lewis acid mediated reactions improves the environmental impact of the synthesis and reduces overall waste. The new route described herein is more efficient, convenient, reliable, and economically more viable when compared to the previously reported linear route.
AbstractIn this paper, the synthesis of the carbon skeleton of cotylenin A aglycone is described. The key reactions, including an intramolecular aldol reaction, an aldol coupling reaction, and a ring-closing metathesis, allow for the effective and stereoselective access to the carbon skeleton of cotylenin A aglycone. The stereochemistry was confirmed by single-crystal X-ray crystallographic analyses of related compounds.
Convergent synthesis of the tetrasaccharide repeating unit of the cell wall lipopolysaccharide of Escherichia coli O40
