6-deoxy-D-galactal

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... 

Anhydro-l,5-dideoxy-SLV3,hino-hex-5-enitol. l,5-Anhydro-2,6-dideoxy- yxo-hex-1-enitol. D-Fucal. 6-Deoxy-D-galactal [134355-03-6]... 

By use of trialkylaluminums a range of alkyl and alkenyl groups can be introduced at C-1 compound 44 can be obtained in 72% yield by treatment of di-0-acetyl-6-deoxy-D-galactal in dichloromethane at -78°C with trimethylalumi-num in the presence of titanium tetrachloride (Scheme 15) [62], and the doubly C-1-substituted 45, required for natural product synthesis, is produced stereo-specifically from tri-O-acetyl-l-C-allyl-D-glucal by a similar methylation procedure [63]. 

The hexosylulose derivative 7c may also be converted into the GDP derivative of colitose (3,6-dideoxy-L-xy/o-hexose, 3,6-dideoxy- L-galact-ose ),161,195 a component of lipopolysaccharides from several enterobacterial strains. Another monosaccharide of this group, ascarylose (3,6-dideoxy-L-arabino-hexose, 3,6-dideoxy- L-mannose ), which is present in Yersinia pseudotuberculosis lipopolysaccharides, was found to be synthesized as the CDP derivative through epimerization and reduction of CDP-6-deoxy-D-xy/o-hexos-4-ulose.168 171... 

Deoxy 4- O - (3-D-galactofuranosyI-L-mannose, G-22 6-Deoxygalactonic acid, F-93 1 -Deoxy-D-galact onojirimycin, H-175... 

Benzamido-l,3,4,5,6-penta-0-benzoyl-D-allitol, A-155 6- O -Benzoyl-1 -deoxy-D-galact i tol, D-123 l-0-Benzoyl-2,3 5,6-di-0-isopropylidene-D-allitol, A-75 6-O-Benzoyl-D-glucitol, G-247... 

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. 

Deoxy-2-[ F]fluoro-D-galactose can be prepared through an addition reaction to tri-O-acetyl-D-galactal (465), but better through Sn2 reaction (K F-Kryptofix 222 in MeCN) of methyl 3,4-0-isopropylidene-2-0-triflyl-6-0-trityl-y -D-talopyranoside (220 see Section 11,2), according to the cold synthesis. 

Nitroglycals65 are excellent Michael-type acceptors,66 where O-, N-, S-, C- and P-nucleophiles can be used as donors.67 An application of this kind of reaction was reported by Schmidt et al. for a new synthesis of 2-deoxy-2-nitro-D-galactose nucleoside 86 and of /V-acetyl-D-galactosamine nucleoside 88, based on addition reactions to 3,4,6-tri-0-benzyl-2-nitro-D-galactal 85 (Scheme 28).68... 

Unsaturated sugars, namely glycals, such as 3,4,6-tri-Oacetyl-l, 5-anhydro-2-dcoxy-D-r//v/-/w7o-hex-1-enetol and the d-/v.yo epimer react with xenon difluoride in the presence of a boron trifluoride-diethyl ether complex to give a mixture of C2 epimeric fluorides.45,46 Tri-O-acctyl-D-galactal treated with xenon difluoride in trichlorofluoromcthane below 5 C forms after hydrolysis (0.5 M HC1) 2-deoxy-2-fluoro-D-galactose in 63% overall yield.47... 

From the oxo reaction of 3,4,6-tri-O-acetyl-D-galactal (36) (after deacetylation of the mixture of products), there was obtained, in almost quantitative yield, 2,6-anhydro-3-deoxy-D-golacto-heptitol (37) and 2,6-anhydro-3-deoxy-D-foio-heptitol (38). - Structural investigations of these anhydrodeoxyalditols paralleled those on the alditols obtained from 3,4,6-tri-O-acetyl-D-glucal. The absolute structures of compounds (37) and (38) were unequivocally established by correlation, as shown, with 2,6-anhydro-3-deoxy-D-gZuco-heptitol (27). Prior structural work" on compound (37), with the aid of periodic acid degradations only, had led to an incorrect, tentative assignment of structure. 

Grynkiewicz, G, Priebe, W, Zamojski, A, Synthesis of alkyl 4,6-di-0-acetyl-2,3-dideoxy-a-D-t/ireo-hex-2-enopyranosides from 3,4,6-tri-0-acetyl-l,5-anhydro-2-deoxy-D-fyjco-hex-l-enitol (3,4,6-tri-O-acetyl-D-galactal), Carbohydr. Res., 68, 33-41, 1979. 

More specifically, tri-O-acetyl-D-gulal has been isolated in low yield from the reaction of tri-O-acetyl-D-galactal and of 1,3,4,6-tetra-O-acetyl-2-deoxy-a-D-Jyxo-hexopyranose with boiling acetic acid (see p. 214), and 4,6-0-benzylidene-3-0-methyl-D-allal has been prepared by reductive desulfurization of 2-thio derivatives (see p. 225). 

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