ALPHA-D-GLYCOSYL-SUBSTITUTED ALPHA,ALPHA-D-TREHALOSES WITH (1-]4)-LINKAGE - SYNTHESES AND NMR INVESTIGATIONS

Two symmetrical trehalose glycosyl 'acceptors' 4 and 6 were prepared and three of the unsymmetrical type, 8, 10, and 11. Glucosylation of symmetrical 'acceptor' 4 gave a higher yield of trisaccharide (44%) than protective-group manipulation, namely via selective debenzylidenation 2 --> 9 or monoacetylation 2 --> 5 which proceeded in moderate yields (33-34%). A comparison of catalysts in the cis-glucosylation of trehalose 'acceptor' 10 with tetra-O-benzyl-beta-D-glucopyranosyl fluoride 13 profiled triflic anhydride ((Tf)2O) as a new reactive promoter yielding 92% of trisaccharide 14, deblocking gave the target saccharide alpha-D-glucopyranosyl-(1 --> 4)-alpha,alpha-D-trehalose. H-1-NMR spectra of most compounds were analyzed extensively. The use of the 1D TOCSY technique is advocated for its time efficiency, if needed supplemented by ROESY experiments.