Mannofuranoside

CioH2904S2 Ethyl 2-S-ethyl-1,2-dithio-a-D-mannofuranoside EDTMAN10 30 452... 

The appearance of free iodine in periodate reaction-mixtures obviously indicates that the iodate formed is being further reduced,84 86 sometimes because of the addition of insufficient oxidant.86 87 This breakdown of iodate to free iodine has been reported as accompanying the a-hydrogen type of oxidation,89 at least as regards the oxidation of those methyl aldohexo-furanosides of which methyl a-D-mannofuranoside is a representative. The... 

The solvolysis of 6-deoxy-2,3-(9-isopropylidene-4-0-methanesuIpho-nyl-a-L-talop3T anose (30), with methanolic sodium methoxide, afforded three products which were identified as l,4-anhydro-6-deoxy-2,3-0-isopropyhdene-a-L-mannopjrranose (33, 58%), methyl 6-deoxy-2,3-0-isopropylidene-a-L-talofuranoside (33, 26%), and methyl 6-deoxy-2,3-0-isopropylidene-a-L-mannofuranoside (34, 12%). Both of the minor... 

In attempting to obtain 2,5-anhydro-D-glucose diethyl dithioacetal, Defaye58 performed the nitrous acid deamination of 2-amino-2-deoxy-D-glucose diethyl dithioacetal (27) under weakly acidic conditions (acetic acid and sodium nitrite), and obtained a principal product later shown59 to be ethyl 2-S-ethyl-l,2-dithio-a-D-mannofuranoside (28). Shortly before, Horton and coworkers60 had reported the forma-... 

B. SynthesiB of a-Methyi Mannofuranoside and p-Methyi Ailofuranoside [38] (Scheme 15)... 

A kinetic study of the methyl glycosidation of D-mannose was also made by Mowery.48 The more stable anomer, the a-D-mannofuranoside, was formed at a higher initial rate (see Table III) the proportions of both furanosides in the final equilibrium mixture was too small to permit accurate comparison of isomer distribution. The conformational stability of the D-mannofuranosides may be compared with that of the D-lyxo-furanosides the furanoid structures are similar, except for the bulky two-carbon group at 04 of the hexoside. This similarity is shown in the very small proportion of n-lyxofuranosides (see Table V) and of D-manno-furanosideo (see Table III) in the final equilibrium mixtures, and also in the initial formation of D-mannopyranosides48 and of D-lyxofuranosides.u... 

It was found122 that 2,3 5,6-di-0-isopropylidene-D-mannose reacts with p-toluenesulfonyl chloride in pyridine, but the only product isolated was the corresponding mannofuranosylpyridinium p-toluenesulfonate. On the other hand, when 2 moles of the sodium salt of 2,3 5,6-di-0-iso-propylidene-D-mannose, dissolved in dry petroleum ether, were treated with one mole of p-toluenesulfonyl chloride, there apparently resulted the nonreducing-disaccharide derivative, 2,3 5,6-di-0-isopropylidene-D-mannofuranosyl 2,3 5,6-di-0-isopropylidene-D-mannofuranoside (a compound later prepared121 by condensation of 2,3 5,6-di-0-isopropylidene-D-mannosyl chloride with 2,3 5,6-di-0-isopropylidene-D-mannose). Presumably, the following reactions had taken place (Ip = isopropylidene) ... 

It was claimed308 that alkaline hydrolysis of methyl 6-deoxy-2,3-0-isopropylidene-4-O-tosyl-n-mannoside (I) gives, by Walden inversion at carbon atom 4, methyl 6-deoxy-2,3-0-isopropylidene-L-talopyranoside (II) and that alkaline hydrolysis of methyl 6-deoxy-2,3-0-isopropylidene-5-0-tosyl-L-mannoside (III) yields,308 by inversion at carbon atom 5, methyl 6-deoxy-2,3-0-isopropylidene-D-gulofuranoside (IV) plus methyl 6-deoxy-2,3-0-isopropylidene-L-mannosid-5,6-een (C). The formation of C has since been confirmed,380 but IV was shown to be800 307 actually methyl 6-deoxy-2,3-O-isopropylidene-L-mannofuranoside (B), and II is indeed methyl 6-deoxy-2,3-0-isopropylidene-L-mannopyranoside (A). Thus, this claim to discovery... 

P. Koll, A. Fortsch, and J. Kopf, Methyl-2,6-anhydro-a-D-mannofuranosid. Eine verbesserte Darstellungsmethode sowie die Bestimmung der Kristall- und Molekulstruktur, J. Carbohydr. Chem., 2 (1983) 189-200. 

P. Koll and H. Komander, Methyl-2,6-anhydro-a-D-mannofuranosid, ein Nebenprodukt der Methanolyse von Methyl-2,6-anhydro-a-D-mannopyranosid, Liebigs Ann. Chem., (1981) 1960-1966. 

Hockett, Nickerson, and Reeder,91 using a very large excess of lead tetraacetate in acetic acid at 20°, observed an oxidation pattern for methyl a-D-mannofuranoside consistent with that noted by Criegee. One mole of reagent per mole was consumed very rapidly, and further oxidation was slow, as expected for the sequence XXV — XXVII. Presence of a small but finite amount of XXVI was thought to account for the slow, continuing oxidation. 

---