Facile Synthesis of β- and α-Arabinofuranosides and Application to Cell Wall Motifs of M. tuberculosis

Abstract

Propargyl 1,2-orthoesters of arabinose are exploited for the synthesis of 1,2-trans furanosides; easily accessible 1,2-trans ribofuranosides are converted to challenging 1,2-cis-arabinofuranosides by oxidoreduction. Utility of these protocols was demonstrated by the successful synthesis of major structural motifs present in the cell surface of Mycobacterium tuberculosis. Key furanosylations were carried out under gold-catalyzed glycosidation conditions.

Chapter 8. Recent advances in gold-catalyzed glycosylation

“…These 1,2-trans and 1,2-cis furanosidations were successfully applied as key steps to the synthesis of hexasccharide 52 as major structural motifs in the cell wall of Mycobacterium tuberculosis (Scheme 10). 22 2.6 Gold(III)-catalyzed glycosidation with 1-ethynylcyclohexanyl glycosyl donors In 2012, after a systematic evaluation of the effect of the substitution groups on the activation of substituted propargyl glycosides (mannopyranosyl, glucosyl and galactosyl donors) with gold catalyst, Hotha and co-workers discovered that the use of gem-disubstituted donors, especially 1-ethynylcyclohexanyl glycolsyl donors (for example 53) increases the reactivity and allows transglycosidation with sugar-based aglycones at room temperature to produce corresponding disaccharides 54 (Scheme 11) in high yields. Thorpe-Ingold like effect accounts for the increased reactivity of gem-disubstitution.…”

Stable Alkynyl Glycosyl Carbonates: Catalytic Anomeric Activation and Synthesis of a Tridecasaccharide Reminiscent of Mycobacterium tuberculosis Cell Wall Lipoarabinomannan

“…A number of glycosyl carbonates, 4j-p,w ere observed to be exemplary donors and afforded various glycosides,d isaccharides,a nd oligosaccharides (products 22-37). [12] Saponification of orthoester 42 under ZemplØn conditions afforded the diol 43,which was converted into disilyl ether 44.G old-catalyzed glycosidation with 4-penten-1-ol, followed by fluoride-mediated desilylation, afforded the n-pentenyl furanoside 45.T reatment with one equivalent of tert-butyldiphenylsilyl chloride (TBDPSCl) and subsequent benzoylation gave the orthoester 46,which upon hydrolysis under gold-catalysis conditions afforded the required hemiacetal 47.F inally,t he treatment of 47 with carbonate 6 in DBUa fforded the desired furanosyl donor 48. [8] Furthermore,c arbonate glucoside 4a was observed to be av ery good donor for the synthesis of azido glucoside 38 in the presence of azidotrimethylsilane (Scheme 7).…”

Total synthesis of mycobacterial arabinogalactan containing 92 monosaccharide units

“…Among a number of innovative glycosyl donors developed by several groups2531323334353637, perbenzyl-protected thioglycoside 13a (ref. 25) and 3,5- O -tetraisopropyldisiloxanylidene-protected thioglycosides 13b , c (ref.…”