Methyl 3,4-0-isopropylidene

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. 

Nucleophilic displacements at carbon atoms adjacent to the ano-meric center of aldopyranosides do not normally proceed satisfactorily, but, surprisingly, treatment of methyl 3,4-0-isopropylidene-2-0-(p-nitrophenylsulfonyl)-a-D-glucoseptanoside with tetrabutylammon-ium fluoride in acetonitrile afforded the corresponding mannoside, from which 2-deoxy-2-fluoro-/3-D-mannopyranose was obtained by subsequent deprotection.153 Whether this is a general property of sep-... 

The stereoselectivity in the Grignard reaction,97 complementary to that in the methyllithium109 and diazomethane156 reactions, of methyl 3,4-0-isopropylidene-a-L-en/thro-pentopyranosid-2-ulose (62), and that between the Grignard and diazomethane reactions of the / ano-mer107 of 62, methyl 2,3-0-isopropylidene-/ -L-en/thro-pentopyranosid-... 

C9H14O5 Methyl 3,4-0-isopropylidene-/3-L-erythro-pentopyranosid-2-ulose22... 

Hot absolute methanol containing p-toluenesulfonic acid effected226 de-acetonation of methyl 3,4-0-isopropylidene-2,6-di-0-tosyl-a-D-galactoside. 

P. Kovac, J. Hirsch, and V. Kovacik, Synthesis and reactions of uronic acid derivatives. Part II. /8-Elimination reactions of some derivatives of methyl-3,4-0-isopropylidene-D-galacturonate, Carbohydr. Res., 32 (1974) 360-365. 

J. S. Burton, W. G. Overend, and N. R. Williams, Branched-chain-sugars. Part II. The introduction of branching into methyl 3,4-0-isopropylidene-/ -l-arabinoside and the synthesis of L-hamamelose, J. Chem. Soc., (1965) 3433-3445. 

Reductive cleavage of hydrazino sugars leads to their amino analogs. Thus, methyl 3,4-0-isopropylidene-2-0-p-tolylsulfonyl- 8-L-arabinopyran-oside was converted through the hydrazino derivative, with Walden inversion,38 38b to 2-amino-2-deoxy-a-i.-ribose hydrochloride.38 The d and... 

Another example in the C-glycosylated, unsaturated hydrocarbon series is methyl 2-deoxy-3,4-0-isopropylidene-2-C-methylene-/3-D-erythro-pentopyranoside (213), obtained90 in 55% yield by the reaction of methyl 3,4-0-isopropylidene-/3-D-eryfhro-pentopyranosid-2-ulose (212) with methylenetriphenylphosphorane n-butyllithium was used as a proton acceptor. Subsequent reduction of 213 with 10% palladium-on-charcoal led to a 7 1 mixture of the 2-epimeric methyl 2-deoxy-2-C-methylpentopyranosides (214 and 215, respectively). In the n.m.r. spectrum of 214, the H-l resonance appeared as a doublet at r 5.62 p.p.m., exhibiting aJia coupling constant of 8 Hz, thus indicating H-2 to be axial and, therefore, the D con-... 

---