Arabinose diethyl dithioacetal, methylation

A detailed comparative study on the benzylidenation of D-arabinose diethyl-dithioacetal with benzaldehyde dimethylacetal and catalytic TsOH or with benzaldehyde in the presence of HCl or ZnCb has been published, and the benzylidenation of methyl a-D-mannopyranoside with benzaldehyde and TsOH has been improved, with yields of acetal 9 >72%." Transacetalation of fully 6-0-pivaloylated a-, P-, and y-cyclodextrins with benzaldehyde dimethylacetal and catalytic camphorsulfonic acid gave mono-benzylidene products 10. Reductive ring-opening (LAH/AIQ3) of compounds 10 afforded predominantly the 2 -0-unprotected derivatives 11. ... 

Scheme 44. Partial fragmentation of n-arabinose diethyl dithioacetal, 2-0-methyl and 3-0-methyl hexose diethyl...

Diamino-2,4-dideoxyarabinose i.-form, D-413 2,3 4,5-Di-0-benzylidene-D-arabinose diethyl dithioacetal, A-852 2,4 3.5-Di-0-benzylidene-D-arabinose diethyl dithioacetal, A-852 l,2 3,4-Di-0-isopropylidene-p-D-arabinopyranose, 1-61 l,2 3,4-Di-0-isopropylidene-p-L-arabinopyranose, 1-61 2,3 4,5-Di-0-isopropylidene-DL-arabinose diethyl dithioacetal, A-852 2,3 4,5-Di-0-isopropylidene-D-arabinose diethyl dithioacetal, A-852 2,3 4,5-Di-0-isopropylidene-L-arabinose diethyl dithioacetal, A-852 2,3 4,5-Di-0 -isopropylidene-D-arabinose, A-850 l,2 3,4-Di-0-isopropylidene-2-C-methyl-p-D-arabinopyranose, M-229 Ethyl 2,5-anhydro-a-L-arabinofnranoside, A-503... 

Other Alkyl and Aryl Ethers.—Selective benzylation of 0-3 of methyl 4,6 O-benzylidene-a-D-mannopyranoside has been noted in the previous section, while 2,3,4,5-tetra-O-benzyl-L-arabinose diethyl dithioacetal and 2,3,4,5-tetra-O-benzyl-D-arabinose dibenzyl and ethylene dithioacetals have been prepared by benzylation of the thioacetals using benzyl chloride and potassium hydroxide. 

At reflux, the action of 3 equivalents of mercury(II) chloride in methanol converts the diethyl dithioacetal of D-glucose into a 5 1 mixture of methyl /3- and a-D-glucopyranoside299 extension of this reaction to the dibenzyl dithioacetal s of L-arabinose, L-rhamnose, and D-galactose afforded, as major products, the methyl /3-l-pyranoside of the L-pentose and the methyl a-pyranosides of the two hexoses, respectively.300... 

Deoxy-[5- H]-L-arabinose has been synthesized from L-arabinose by reduction (NaBD4-DMSO) of the 5-tosylate of its diethyl dithioacetal, and converted into [3 - H] biopterin. Methyl oligobiosaminide (17), its 6-hydroxy-derivative (18), and their 2- and 3-deoxy-analogues (19) and (20) have been synthesized by coupling 4-amino-4-deQj -hexose residues with the pseudo-sugar epoxide (16) (Scheme 3). While almost no glycosidase... 

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