Pyranoid Derivatives

An extensive (re)investigation of the additions of IN3, Br2 and Br2/MeOH to tri-0-acetyl-D-glucaI and tri-O-benzyl-D-galactal has been reported. The results are in keeping with previous knowledge. The enolone 3 when treated with 

Carbohydrate Chemistry, Volume 34 The Royal Society of Chemistry, 2003 

Reagents i, ArNCO, DBU then oiodoxybenzoic acid, anhydrous conditions ii, as for i. wet conditions 

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Nevertheless, there are various entry reactions into simple pyranoid derivatives (Scheme 2.10) with which to exploit their industrial application potential. 

Lichtenthaler, F. W. Klotz, J. Flath, F. J. Acylation and carbamoylation of D-liuctose acychc, furanoid and pyranoid derivatives, Liebigs Ann. Chem., 1995, 2069-2080. 

Tables V-LVII detail H and F shift and coupling information, and Tables LVIII to LXXI incorporate the C-n.m.r. data. The data within this compilation are arranged according to the following outline hexoses prior to pentoses, followed by anhydro sugars, sugar acids and lactones, amino sugars (and their synthetic, A -containing precursors), mono-, di-, and tri-deoxy sugars, branched derivatives, ketoses, polyfluorinated monosaccharides, and, finally, difluorinated amino sugars. Within this compilation, and even within each table, pyranoid derivatives are listed prior to their furanoid counterparts, hexoses prior to pentoses, functionalized prior to deoxy compounds the arrangement within each sub-table is made alphabetically.

Finally, this obituary and retrospective survey could not close without a significant mention of Richardson s celebrated rules for nucleophilic replacement of tosylates, mesylates, and halo groups by charged nucleophiles in carbohydrate pyranoid derivatives. They emanated out of his early studies at Reading on the preparation of... 

The aryl aldofuranosides show a greater lability to alkali than the alkyl aldofuranosides. Phenyl 0-n-xylofuranoside is very labile to alkali.82 Treatment of 2-naphthyl 0-D-glucofuranosidurono-6,3-lactone with dilute alkali opens the lactone ring, and rapid hydrolysis occurs.40 Ishidate and Matsui81 noted that p-nitrophenyl 0-D-glucofuranosidur ono-6,3-lactone is most sensitive to alkali, the amide next, find then the pyranoid derivatives toward acids, the relative sensitivities of the lactone and the amide are reversed. 

This factor is shown to be very important in several of the examples given in Section II the compounds described in Section 11,2 showing enhanced activity at C-5, those in 11,6 enhanced activity at C-l, and those in 11,5, enhanced activity at C-l or C-5, according to whether the carbonyl or oximo groups are at C-2 or C-4 of pyranoid derivatives. Captodative radical stabili-... 

Pyranoid derivatives. Mg values of, 29 Pyranoses, conformation of, 13, 14 Pyranosides, methyl, molecular rotations of, 25... 

Solutions of free 6-amino-5-deoxy-D-xylose may also be obtained by catalytic hydrogenolysis of the benzyloxycarbonyl group from ihe pyranoid derivative (31), and by the reduction of 5-azido-5-... 

Cicero, D, Varela, O, de Lederkremer, R M, Synthesis of furanoid and pyranoid derivatives of 6-deoxy-4-thio-D-galactose, Tetrahedron, AL, 1131-1144, 1990. 

The chlorosulfated glycosyl chloride 60 is converted into 2-chloro-2-deoxy-a-D-lyxopyra-nosyl chloride 61 when treated with aluminum chloride (O Scheme 34) [58]. This reaction proceeds via an initial intramolecular displacement of chlorosulfate at C-2 by the anomeric chlorine atom, followed by the chloride ion attack at the more highly reactive center (C-1). Pyranoid derivatives having a chlorosulfonyloxy group in a frawi -diaxial relation with a ring proton, such as 62, may undergo an elimination reaction to yield the unsaturated compound 63 (O Scheme 35) [59]. 

The special electronic structure of the anomeric center in pyranoid derivatives results in experimentally significant differences in molecular geometry (e.g., as reflected by bond lengths and valence angles) about the anomeric carbon atom between a- and 0-pyranoses and a- and /3-pyranosides. In the article by Jeffrey, a discussion of the structural properties of the anomeric center in pyranoses and pyranosides is given, and a comparison is made of crystallographic data of some carbohydrates with the results of theoretical calculations performed on model compounds. Paulsen and co-workers also present x-ray crystallographic data in their discussion of some aspects of the conformational analysis of pentopyranosyl acetates, benzoates, and halides, in comparison with extensive conformational data compiled by Durette and Horton for these compounds in solution. 

Irradiation of pyranoid derivatives produces a radical at the anomeric centre. In the presence of bromine or N-bromosuccinimide, the chloride of the peracetyl-... 

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