Galactopyranose irradiation

When the esters listed in Table IX are irradiated, typical carbonyl reactions result that is, each of these compounds (22-27) experiences both a-cleavage and hydrogen-abstraction reactions. For the esters of l,2 3,4-di-0-isopropylidene-a-D-galactopyranose (22-26), the hydro-gen-abstraction reaction is internal, and leads69 to a Type II reaction... 

The photochemical reactions of xanthides are quite complex. They are solvent-, concentration-, temperature-, wavelength-, and time-de-pendent.130 The most thoroughly studied of these compounds is compound 64, whose irradiation (through a Corex filter) in cyclohexane under nitrogen produces tetrasulfide 69 (37% yield), xanthate 70 (35%), l,2 3,4-di-0-isopropylidene-a-D-galactopyranose (71, 13%), sulfur, and carbonyl sulfide. Irradiation of a dilute solution of 64 produced only 70 (in 74% yield). The most intriguing finding from irradiation of the xanthides 64-66 is the fact that 66 produces a xanthate... 

The o-iodobiphenylyl ethers, 92 and 93, of l,2 3,4-di-0-isopropyli-dene-a-D-galactopyranose and l,2 5,6-di-0-isopropylidene-a-D-glu-cofuranose, respectively, have been irradiated in 2-propanol and in 2-... 

Ultraviolet irradiation43 of a methanolic solution of compound 3 in the presence of alkali led to its rapid, almost quantitative, conversion into l,2 3,4-di-0-isopropylidene-a-D-fucopyranose (5) an excellent yield of 5 was also obtained44 by irradiation of a solution of 6-O-acetyl-l,2 3,4-di-0-isopropylidene-a-D-galactopyranose (6) in aqueous hexa-methylphosphoric triamide. 

Oscarson et al. [5] found that benzoylation of 1 is often very slow when conventional methods are used, but it is dramatically accelerated under micro-wave activation. Benzoylation of selected substrates, for example acetonated a-D-galactopyranose and benzylidene 4,6-protected a-D-glucopyranose, which are not stable in acidic conditions, was performed by Cleophax et al. [13] under the action of microwave irradiation in a monomode system with methyl benzoate for 4-15 min. 

Deoxysugars. A soln. of l,2 3,4-di-0-isopropylidene-a-D-galactopyranose 6-di-methylthiocarbamate in methanol irradiated 200 hrs. with a 450 w. Hg-arc lamp -> 6-deoxy-l,2 3,4-di-0-isopropylidene-a-D-galactopyranose. Y 25% 35—45% on reconverting and recycling the original alcohol obtained as by-product. F. e. s. R. H. Bell, D. Horton, and D. M. Williams, Chem. Commun. 1968,323. 

Deoxy-l,2 3,i<-di-0-isopropylidene-a-D-galactopyranose has been obtained in Q5% yield by irradiation of the corresponding 6- -acetate. Photolytlc deoxygenations of the 2-6-dlpivaloates (1) have provided the 2,6-dideoxyhexosldes (2) in yields ... 

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