Galactopyranose isolation

From the rearrangement of tetra-O-acetyl-2-hydroxy-D-galactal in boiling acetic acid it was possible to isolate l,2,4,6-tetra-0-acetyl-2,3-dide-h.ydro-3-deoxy-a-jy-threo-hexose (32) (58%) and a small amount of 1,2,3,4,6-penta-O-acetyl-jS-D-galactopyranose. In the reaction mixture the presence of some a-pentaacetate was demonstrated chromatographically but NMR spectroscopy indicated no resonances corresponding to the / anomer of compound 32. These spectral measurements indicate that compound 32 constituted 80% of the mixture of products. 

In fact, other studies have shown that TMSOTf catalyzes the glycosylation of a silylated acceptor with a silylated hemiacetal donor [49]. Nudel man s procedure was applied to the synthesis [1-glucuronide 30, isolated in 57% yield. Kiyoi and Kondo have applied the TMSOTf activation protocol to protected L-fucose hemiacetal donors for glycopeptide synthesis and obtained glycopeptide fragment 31 in 74% yield (a p, 20 1) [50], Posner and Bull have developed a procedure that uses excess TMSOTf in the presence of molecular sieves (SYLOSIV A4) to synthesize various l.l -linked disaccharides such as the galactopyranose dimer 32 [51,52]. 

The telomerization of two other protected aldoses, 13 (2,3,4-tri-O-acetyl-L-arabinopyranose) and 14 (2,3,4,6-tetra-(9-benzyl-D-galactopyranose) (Fig. 8), has been briefly examined corresponding adducts were isolated with yields up to 85% from 13 in DMF [21], and 91 or 93% from 14 in CH2CI2 and THF respectively [22],... 

Similarly-constituted glucomannans have been isolated from various species of iris seeds107 and lily bulbs,108 the polysaccharides containing D-glucose and D-mannose residues in the proportions 1 1.1 and 1 1.9, respectively. The iris-seed glucomannans also contain a small proportion of D-galactopyranose end-groups.107... 

The first synthesis of 2,3,4-trimethyl-D-galactose, which had previously been isolated from the hydrolysis products of methylated galac-tosans, was achieved by McCreath and F. Smith.20 1,6-Anhydro-D-galactopyranose, treated with dimethyl sulphate and alkali, underwent easy methylation and the resulting crystalline 2,3,4-trimethyl-l,6-anhydro-D-galactopyranose was conveniently hydrolyzed to the free sugar hydrate. 

M. Jaseja, A. S. Perlin, O. Dubinsky, D. Christiaen, S. S. (Malis) Arad, andR. Glaser, N.m.r. structure determination of 3-0-(a-D-glucopyranosyluronic acid)-L-galactopyranose, an aldobiuronic acid isolated from the unicellular red alga Rhodella reticulata, Carbohydr. Res., 186 (1989) 313-319. 

Haworth, Porter, and Waine examined the reaction of D-galactose and of D-xylose with phosgene in acetone, and isolated, respectively, 6-0-(chloroformyl)-l,2 3,4-di-0-isopropylidene-D-galactopyranose (XIV) and 1,2-0-isopropylidene-D-xylofuranose 3,5-carbonate (X). The reactive chloroformyl compound could be converted to the 6-0-(phenylaminocar-bonyl) derivative XXXVI by treatment with aniline, or to the 6-0-(meth-oxycarbonyl) derivative with methanol, and its possible use in the optical... 

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