Galactofuranoside preparation

Crystalline 1,4-anhydro-D-sorbitol is of much more recent origin than 1,4-anhydro-D-mannitol, inasmuch as its preparation was first recorded in 1946.10 It was obtained by the restricted dehydration of D-sorbitol and has been given the trivial name arlitan. Two groups of workers simultaneously effected proof of its constitution. Hockett and coworkers11 treated the anhydride with lead tetraacetate and since its rate of oxidation coincided with that of ethyl D-galactofuranoside and since one molecular proportion of formaldehyde was formed, the authors concluded that the ring must involve Cl and C4 of a hexitol chain. Assuming that no other carbon atoms are involved, sorbitan is either 1,4-anhydro-D-sorbitol or 1,4-anhydro-D-dulcitol (Walden inversion at C4 of the sorbitol molecule). They therefore synthesized 3,6-anhydro-D-dulcitol (enantio-morphous with 1,4-anhydro-L-dulcitol) but found it to be different from arlitan. 

Wolfrom and coworkers88-71 were able to prepare various 1-thio-a-D-galactofuranosides, generally isolated as the acetates, after purification by column chromatography. Thus, the Pacsu and Wilson method gave sirupy ethyl 1-thio-a-D-galactofuranoside, and a crystalline acetate. This product was also obtained by treatment of the dithioacetal with dilute hydrochloric acid and then mercuric oxide. Ethyl 2-acetamido-2-deoxy-l-thio-a-D-galactofuranoside was prepared in 32% yield, and the /3-d anomer in 3% yield. 

Several oligosaccharides containing o-fructofuranose residues have been prepared,121 as well as an a-D-glucopyranosyl D-galactofuranoside.124... 

A series of similar changes was observed on treatment of 2-desoxy-D-galactose with ethanolic hydrogen chloride and it was possible to prepare ethyl 2-desoxy-a/8-D-galactofuranoside and ethyl 2-desoxy-aj8-D-galacto-pyranoside. Essentially similar results were observed with desoxy-pentoses, and the methyl glyco-furanosides and -pyranosides of 2-desoxy-L-ribose were prepared.141... 

The 2,3,5,6-tetramethyl-D-galactofuranose was accurately characterized in 1924-27 and was prepared by the acid hydrolysis of fully methylated a,/3 methyl D-galactofuranoside.lb... 

Arasappan and Fraser-Reid described the preparation of w-pentenyl galactofuranosides and evaluated their prospects as glycosyl donors (O Scheme 21) [81]. Fischer glycosidation of D-galactose under kinetic conditions using -pentenyl alcohol and DMSO as co-solvent [82]... 

The formation of C-P bonds by the radical addition of phosphines to exocyclic carbohydrate alkenes was originally reported by Whistler [109], who demonstrated that irradiation of alkene 171 in the presence of phenylphosphine afforded the phosphine oxide 172 (Scheme 29). Sinay [110] prepared the gem-difluoro-C-galactofuranoside 173 by phosphonyl radical addition to gem-difluoroalkene 174 during studies related to the preparation of potential inhibitors of the enzyme UDP-galactofuranose mutase. 

Otherwise p-galactofuranosides can be made from the galactono-y-lactone. By standard chemistry the D-fucoside 22 was made, and the 0-benzoylated glycosyl acetate was used to prepare a 6-deoxy-p-D-galactofuranosyl-(l->3)-D-man-nose. By standard synthetic steps 2-deoxy-pentofuranoside23 was converted to the furanoid 24 and hence to the pyranoid thioglycoside 25 for introducing L-axenose into various antibiotics. ... 

Methyl 2,3,5,6-tetradeoxy-2,3,5,6-tetrathio- 8-L-galactofuranoside and -0(-D-altropyranoside have been prepared by the routes shown in Schemes 2 and 3. The syntheses of 6-deoxy-4-thio-a-D-talopyranose and - 3-L-allopyranose have been achieved by applying to D-mannose the methods developed in the D-glucose series (see Vol. 12, p. 94). The unsaturated 4-thio-derivatives (6) and (7) were obtained from the 4-ulose (8) by treatment with phosphorus pentasulphide in pyridine followed by acetylation. ... 

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