Sulfate, Halogen Compounds, and Oxirane

The two primary hydroxyl groups in maltose and its derivatives show a large difference in reactivity. On selective tritylation, /3-maltose,238 benzyl /3-maltoside,239 and methyl 3-0-(methylsulfonyl)-/3-maltoside127 all gave mainly 6 -0-trityl compounds. Tritylation of cyclohexaamylose130 and amylose132,240 yielded the expected 6-0-trityl derivatives. 

Reaction of methyl 4,6-O-benzylidene-a-D-glucopyranoside with methyl iodide253 or with tetra-O-acetyl-a-D-glucopyranosyl bro- 

It is of interest that reaction of methyl, benzyl, and p-nitrophenyl 2-acetamido-4,6-0-benzylidene-2-deoxy-/3-D-glucopyranosides, and also the corresponding methyl a-D-glucopyranoside derivative, with ( )-2-chloropropionic acid gave, in preponderant yields, the respective 3-0-(D-l-carboxyethyl) derivatives257 only from the last-mentioned reaction was a significant amount of the 3-0-(L-l-carboxy-ethyl) derivative isolated. 

Haworth methylation of methyl /3-D-glucopyranoside and its 4-benzyl and 4-(tetrahydropyran-2-yl) ethers was investigated in connection with partial-methylation studies on cellulose.267 For the unsubstituted glycoside, the ratios of relative rate-constants k2 k3 k4 k were estimated to be 8 2 1 8, and, for the 4-ethers, it was found that ke k2 k3 best agreements between calculated and experimental yields were found with the assumption that the rate constant for reaction at HO-3 is doubled when HO-2 is substituted. Later methylation studies,268 performed to low degrees of substitution, with analysis by gas-liquid chromatography, gave k2 k4 k3 for the reactivity 

Methyl a-D-glucopyranoside may be converted,271 in a remarkably selective reaction, into its 2,4,6-tribenzyl ether (in 62% yield) on treatment with three molar equivalents of sodium hydride in benzyl chloride at 110°, a substitution pattern that might have been predicted in view of the low, relative reactivity of HO-3 towards alkylation in the mechanistically related, Haworth procedure.268 Similar, selective benzylations have also been achieved on partially substituted derivatives of methyl a- and /3-D-galactopyranoside272 and on methyl 6-deoxy-a-L-galactopyranoside62 in all of these, an unexpectedly high relative-reactivity of HO-4 (ax) compared to that of HO-3 (eq) was noted, indicating that steric factors are not the sole influence on reactivity in these cases. Nevertheless, the primary hydroxyl 

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