Glucal 6 - deoxy - 3 - 0 - methyl

On their side, Yin and Linker [216] made use of a 2-C-branched hexopyranoside, the synthesis of which was achieved by addition of dimethyl malonate to tri-O-benzyl-D-glucal (TUPAC name 3,4,6-tri-0-benzyl-l,5-anhydro-2-deoxy-D-araZtino-hex-l-enitol, Scheme 45) [217], Thus, saponification of the 2-C-[bis(meth-oxycarbonyl)]methyl derivative 184 to the corresponding malonic acid 185 was followed by heating in refluxing toluene. This led to decarboxylation and lactoniza-tion giving 186. The method was optimized and applied to the synthesis of pentoses and disaccharides. 

Simple alkylation can be accomplished by use of trialkylaluminums which, with Lewis acids, afford 1-C-alkyl products such as 90, available in 72% yield by reaction between di-O-acetyl-6-deoxy-D-galactal and trimethylaluminum in the presence of titanium tetrachloride in dichloro-methane at —78 °C.109 Importantly, the reaction can also be applied to 1-alkylglycals, also with high stereoselectivity, so that the doubly substituted compound 91 can, for example, be made by allylation of tri-O-acetyl-l-C-methyl-D-glucal. Its C-l epimer is available by C-methylation of the 1-C-allylglucal.110... 

A stereospecific reduction of a pseudoglycal has been used to prepare the same isomer.23 Reduction of methyl 4,6-0-benzylidene-2,3-dideoxy-/3-D-erythro-hex-2-enopyranoside (6) with lithium aluminum deuteride led to the stereospecific synthesis of 4,6-0-benzylidene-3-deoxy-D-glucal-3(S)-d (7), which, after oxidation with osmium tetra-oxide-periodate followed by debenzylidenation, gave 2-deoxy-D-erythro-Tpentose-2(S)-d (2-deoxy-2-deuterio-D-arabinose) (8). Reduc-... 

Addition of dichlorocarbene, produced by treatment of ethyl tri-chloroacetate with sodium methoxide, to 3,4,6-tri-O-methyl-D-glucal gave, apparently, one product (gas-chromatographic analysis) in 82% yield. By stereochemical analogy with epoxidations, the product was considered to be l,5-anhydro-2-deoxy-l,2-C-(dichloromethylene)-3,4,6-tri-O-methyl-D-g/j/cero-D-ido-hexitol (21). Demethylation was brought about with boron trichloride at—70°, to give atriol from which a crystalline tribenzoate was obtained and reaction with lithium aluminum hydride caused reductive cleavage of the carbon-chlorine bonds.36 A similar addition was applied to 3,4-unsaturated furanosyl compound (see p. 247). 

From the reaction with tri-O-acetyl-n-glucal, after replacement of the ionic acetate by chloride, methyl 3,4,6-tri-0-acetyl-2-(chloromercuri)-2-deoxy-d-D-glucopyranoside (41) was first isolated in 38% yield. The... 

Acetoxylation of the double bond is caused by lead tetraacetate thus, compound (123, R = Ac, Ri = OMe, Rj = H), gives crystalline methyl 5-acetoxy-tetra-0-acetyl-/8-D-glucopyranoside (126), which is hydrolyzed, on standing at room temperature in aqueous solution, to tetra-O-acetyl-n-a 2/lo-hexos-5-ulose (124, R = Ac, Ri = OAc). By means of this reaction, D-glucose has been converted, by way of 2-acetoxy-tri-O-acetyl-D-glucal and its main hydrogenation-deacetylation product, namely, styracitol, into 1,5-anhydro-2,3,4-tri-0-benzoyl-6-deoxy-D-lya o-hex-5-enitol (127), and thence, by acetoxylation and de-esterification, into n-fructose (128) ... 

CioHmO 214.218 Syrup. Mg -76.4 (c, 0.28 in CHCI3). 3-Me 3-O-Methyl-D-rhamnal. 6-Deoxy-3-O-methyl-D-glucal C7H12O3 144.17... 

Deoxy-3-0-methylfucose, D-638 6-Deoxy-3-0-methyl-D-gaJactose, F-163 6-Deoxy-3-0-methyI-L-galactose, F-163 6-Deoxy-3-O-methyl-D-glucal, D-679 6-Deoxy-3-O-methyl-L-glucal, D-679 6-Deoxy-3-0-methyl-D-glucose, D-142... 

Acetyl-6-deoxy-3-0-methyl-D-glucal, D-679 6-0 -Acetyl-3,4-di-O -benzyl-D-galactal, G-1 4-0 -Acety 1-3,6-di-O -benzyl-D-galactal, G-1... 

O -Acety l-6-deoxy-3- O -methyl-D-glucal, D-679 4-C-Acetyl-2,6-di(leoxy-x j /o-hexose L-form, A-18... 

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