Galactofuranoside ethyl

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. 

An entropy value for the acidic hydrolysis of ethyl 0-D-galactofuranoside was reported by Overend and coworkers.136 The negative value (—7.1 e.u.) was interpreted as being diagnostic of an A-2 mechanism, in contrast to the positive values (+13.7 e.u., mean value) and A-l mechanism found for a large number of pyranosides. The proposed intermediate is shown in formula (34). It was considered that the planar, furanoid ring is capable of... 

In contrast, ethyl /J-D-galactofuranoside (43) is oxidized at a lower but steadier rate141 more than two moles of oxidant are consumed per mole, and one mole of formaldehyde is formed. The 5,6-glycol is attacked first, to give (44), and then the tram-2,3-glycol is attacked, to afford the trialdehyde (45). Compound (44) cannot give a hemiacetal. The consumption... 

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... 

With proper protection of certain hydroxyl groups, a desired degradation can take place. 3,4 5,6-Diisopropylidene-D-mannitol treated with sodium periodate in water at 0-5 °C for 30 min furnishes an 89% yield of 2,3 4,5-diisopropylidene-D-arabinose [1153]. Ethyl 2-acetamido-2-deoxy-1-thio-a-D-galactofuranoside yields 80% of a 4-formylthioacetalfuranoside on oxidation with an aqueous solution of metaperiodate at 0-3 °C (equation 300) [762],... 

D-glucose mixed acetal, at least in the anomeric form employed, is not the probable intermediate in the formation of ethyl a-thio-D-glucofuran-oside from D-glucose diethyl mercaptal but that the mixed acetal is the probable intermediate in the formation of ethyl j3-D-galactofuranoside from D-galactose diethyl mercaptal. 

The D-galactopyranoside ring seems to be essential. Thus, o-nitro-phenyl -D-galactofuranoside could not be hydrolyzed by the E. coli enzyme. Ethyl /3-D-galactofuranoside was not hydrolyzed by the calf-intestine enzyme. 

Ethyl 2,3,5,6-tetra-0-acetyl-/3-D-galactofuranoside was obtained by treatment of 2,3,5,6-tetra-O-acetyl-D-galactofuranose with ethyl iodide in the presence of silver oxide.173... 

The intermediate (16) postulated by Lindberg should be formed from both furanosides and pyranosides, and both of these classes of compound should, therefore, give the same products. The only example thus far studied is the acetolysis of ethyl jS-n-galactofuranoside tetraacetate, which gives jS-D-galactofuranose pentaacetate as the only product isolated after a very rapid reaction. 

Many investigations have shown that furanosides are hydrolyzed faster than pyranosides, and acid-catalyzed hydrolysis of furanosides has been discussed in detail by Green. Additional discussion is given in Section III,la. Overend and coworkers have determined the entropy of activation for one furanoside, ethyl 3-D-galactofuranoside, and found it to be... 

Synthesis from o-galactose (-)-Anisomycin (1) has been synthesized" from D-galactose by conversion firstly to ethyl 2,3-di-0-benzyl-(3-D-galactofuranoside... 

The rapid formation of one mole of formaldehyde when one mole of the ethyl 1-thio-a-D-glucoside of Schneider and Sepp is oxidized with a 5-molar excess of periodate provided evidence for the furanoid ring in this compound, and the 2-molar uptake of oxidant indicated cleavage between C-5 and C-6, and, probably, between C-2 and C-3. Further oxidation, presumably at the sulfur atom, occurred on oxidation for longer than one hour. Similar results were observed with ethyl 1-thio-a-D-galactofuranoside and with ethyl 1-thioglycosides of 2-acetamido-2-deoxy-D-galactose. ... 

Once again, furanosides can be distinguished from pyranosides. The peak at m/e 204 in the mass spectrum of ethyl /3-n-galactofuranoside tetra-O-trimethylsilyl ether 36 is drastically reduced in relative intensity compared to the mass spectra of 34 and 35 (Scheme 36). In addition. 

Et glycoside, tetra-Ac Ethyl 2,3,4,6-tetra-O-acetyl-I-thio-a-D-galactofuranoside C,6H2409S 392.426 Cryst. (Et20/petrol). Mp 51°. Md +118 (CHCI3). 

Et glycoside, 2,3,5S,6-tetra-Ac Ethyl2,3,6-tri-0-acetyl-5-S-acetyl-5-thio-P-D-galac-tofuranoside. Ethyl 2-0,5-0,5-S, d-O-tetraacetyl-p-D-galactofuranoside C16H24O9S 392.426 Cryst. (MeOH). Mp 61°. [a]o -69.7 (c, 1.3 in CHCI3). 

Ethyl 2,3,4,5-tetra-O-acetyl-D-arabinonate, A-825 Ethyl 3,4,5,6-tetra-0-acetyl-2-deoxy-D-ara6mo-hexonate, D-187 Ethyl 2-0,3-0,5-5,6-0-tetraacetyl-p-D-galactofuranoside, T-66 Ethyl 2,3,4,6-tetra-O-acetyl-a-D-galactopyranoside, E-24 Ethyl 2,3,4,6-tetra-O-acetyl-a-D-glucopyranoside, E-25 Ethyl 2,3,4,6-tetra-O-acetyl-p-D-glucopyranoside, E-25... 

---