4-O-Acetyl-3-O-tert-butyldimethylsilyl-l-rhamnal: a building block in the stereoselective synthesis of 2-deoxy-α-l-rhamnopyranosides

Catalytic Glycosylations in Oligosaccharide Synthesis

“…Wandzik and Bieg used TPHP for the glycosylation using L-rhamnals. 521 The reactions were again found to be α-selective (5:1 α/β), which could be further enhanced (12:1 or better) by having a bulky protective group on the 3-O-position and acetyl on the 4-Oposition. A variation of the catalytic system, using triphenylphosphine in combination with TMSI, was found by Cui et al 522 Several disaccharides were prepared from perbenzylated galactal and glucal, by using 5 mol % of the catalyst.…”

“…The polymer-bound dephenylphosphane hydrobromide was, like TPHB, found to suppress the undesired Ferrier reaction and to give high selectivity in the glycosylations using glycals. Wandzik and Bieg used TPHP for the glycosylation using l -rhamnals . The reactions were again found to be α-selective (5:1 α/β), which could be further enhanced (12:1 or better) by having a bulky protective group on the 3- O -position and acetyl on the 4- O -position.…”

pTSA/[bmim][BF4] Ionic Liquid: A Powerful Recyclable Catalytic System for the Synthesis of α-2-Deoxyglycosides

“…For instance, they can be synthesized from 2-iodo-2-deoxyglycoside, followed by dehalogenation [5,6]. The acid-catalyzed addition to glycals represents the most direct method that can be operated under various conditions, including hydrogen bromide [7], triphenylphosphine hydrogenbromide [8][9][10][11][12], Dowex-50 [H ? ] [13], CeCl 3 and LaCl 3 hydrates in combination with NaI, [14,15], TMSOTf-NEt 3 [16,17], BCl 3 [18], ceric ammonium nitrate [19], GaCl 3 [20] and Rhenium(V) complexes [21].…”