Total Synthesis of Marine Glycosphingolipid Vesparioside B

Abstract

The first total synthesis of a major component of marine glycolipid vesparioside B ( Scheme 1 , 1, R1 = n-C22H45, R2 = n-C14H29) has been accomplished through a convergent [4 + 3] coupling strategy. Key steps included stereoselective installment of a set of challenging 1,2-cis-glycoside bonds. A 2-quinolinecarbonyl-assisted α-galactosylation and a novel β-arabinosylation were developed, respectively, to synthesize the α-galactofuranosidic and the β-arabinopyranosidic linkages. Furthermore, a 4,6-O-benzylidene-controlled α-galactopyranosylation reaction allowed the efficient connection of the left tetrasaccharide donor 2 with the right disaccharide lipid acceptor 3, hence leading to the total synthesis of 1.

Stereoselective Synthesis of a Tetrasaccharide Fragment from Cellulosome Produced by Clostridium thermocellum

“…The preparation of synthons 2 , 3 b , and 5 was carried out as illustrated in Scheme . The synthesis of the Gal f thioglycoside 2 began with the known ethyl β‐D‐thio‐galactofuranoside ( 6 ) . This compound was easily converted into 5,6‐diol 7 in 82% yield over three steps: protection of 5,6‐OHs as a isopropylidene acetal, di‐ p ‐methoxybenzylation at C2 and C3 positions, and deprotection of the 5,6‐ O ‐isopropylidene group.…”

Phenanthroline‐Catalyzed Stereoretentive Glycosylations

“…The yield could be improved with use of the acetyl protecting groups ( 22 : 84 %). The diacetyl l ‐arabinose was compatible with a C4 hydroxy group to afford α‐ 23 . A similar trend was observed with d ‐arabinose ( 24 – 27 ).…”

Synergistic Glycosylation as Key to the Chemical Synthesis of an Outer Core Octasaccharide of Helicobacter pylori

“…[9] Recently, Monteiro et al demonstrated the potentialo faLPS-based vaccine against H. pylori,i nw hich the conserved core undecasaccharide [9b, 10] 1 (Figure 1) wasi dentified as ap romising antigen for the development of ag lycoconjugate vaccine targeting all strains. [13] Convergent strategies can focus either on a[ 4 + +4] or a[ 3 + +5] key coupling. [11d, 12] The outer core octasaccharide portion of core undecasaccharide 1 is the key synthetic target.…”