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3.4.6- Tri-O-benzyl-D-glucal

Tri-O-benzyl-D-glucal (97%) was purchased from Aldrich Chemical Company, Inc. and was used as supplied without further purification. [Pg.120]

Starting from 3,4,6-tri-O-benzyl-D-glucal epoxide 93 (Scheme 31), a-C-glycosyl compounds 94 are obtained in good stereoselectivity by treatment with a lithium acetylide and zinc chloride.103... [Pg.51]

In addition, Wipf and co-workers104 have used silver(i)-catalyzed addition of zirconocenes to 3,4,6-tri-O-benzyl-D-glucal epoxide 93 for the stereoselective synthesis of a-C-glucosyl compounds 95 and 96 following a similar mechanism as in the reaction with organoaluminium and organoboron reagents (Scheme 32). [Pg.51]

The first addition of nitroalkanes to glycals was recently described. It involved a radical mediated addition of nitromethane to tri-O-benzyl-D-glucal (48) in the presence of CAN and KOH and methanol as solvent, to give the diastereomeric mixture 49 + 50 (Scheme 18).42... [Pg.178]

M. Ganesan and N. G. Ramesh, A new and short synthesis of naturally occurring 1-deoxy-L-gulono-jirimycin from tri-O-benzyl-D-glucal, Tetrahedron Lett., 51 (2010) 5574-5576. [Pg.297]

On their side, Yin and Linker [216] made use of a 2-C-branched hexopyranoside, the synthesis of which was achieved by addition of dimethyl malonate to tri-O-benzyl-D-glucal (TUPAC name 3,4,6-tri-0-benzyl-l,5-anhydro-2-deoxy-D-araZtino-hex-l-enitol, Scheme 45) [217], Thus, saponification of the 2-C-[bis(meth-oxycarbonyl)]methyl derivative 184 to the corresponding malonic acid 185 was followed by heating in refluxing toluene. This led to decarboxylation and lactoniza-tion giving 186. The method was optimized and applied to the synthesis of pentoses and disaccharides. [Pg.53]

It is also important to point out that the directing ability of basic groups is not limited to alcohols (or, more accurately, zinc alkoxides). Esters and ethers (benzyl, THP, MOM, MEM etc.) can also direct the cyclopropanation reaction. The cyclopropanation of tri-O-benzyl-D-glucal produced the corresponding syn cyclopropane in high yield... [Pg.259]

Oxidation of glucaJs to lactones.6 3, 4, 6-Tri-O-acetyl-D-glucal (1) is oxidized to the unsaturated lactone 2 in 78% yield by PCC. In contrast, tri-O-benzyl-D-glucal (3) is oxidized without elimination to the saturated lactone (4). [Pg.231]

In the case of tri-O-benzyl-D-glucal, entirely different chemistry is observed, with the initially formed cation 102 abstracting a hydride ion from the 0-6 benzyl group to give the 3-deoxy species 103. Intramolecular addition to C-2 affords 104 and the initially cleaved benzoyloxy group adds to C-l to give the unusual bicyclic 105 in 45% yield (Scheme 12).120... [Pg.78]

Preparation of IZnCH2l from EtZnl by an alkyl exchange reaction cyclopropanation of tri-O-benzyl-D-glucal... [Pg.272]

Weigh tri-O-benzyl-D-glucal into the dry one-neck, round-bottomed flask, flush with argon, and add dichloromethane (10 mL). [Pg.274]

From tri-O-benzyl-D-glucal (99), a mixture of /3-D-gluco- (129) and a-d-manno (130) pyranosyl azides was obtained.68,69 The same regioselectivity, affording 129 and 130 in similar proportions, was observed when N-phenylselenophthalimide (N-PSP) was employed instead of PhSeCl in the presence of sodium azide.68 The same outcome was observed with the rham-nal derivative 128, which afforded 131 and 132, whereas only isomer 133 was detected in the H NMR spectrum of the product of addition to glycal 104,69... [Pg.163]

Conversely, by method A, tri-O-benzyl-D-glucal was converted to a mixture of 2-deoxy-2-phenylseleno-/J-D-gluco- and -a-D-mannopyranosyl azide ( ll NMR) by a trarw-Markovnikov addition. [Pg.721]

The addition of A,V-dibromobenzencsulfonamidc to hexose-derived glycals afforded, after reduction of the N —Br bond of the initial adducts, a mixture of diastereomeric 2-bromo-l-phenylsulfonylamino derivatives913 b. In the case of tri-O-benzyl-D-glucal the diastereoselectiv-ity in favor of the diaxial adduct 7 was improved by the alternative procedure using iodonium di-.cyw-collidine perchlorate and benzenesulfonamide (see Section 7.2.6.1.4.). [Pg.779]

The adduct derived from tri-O-benzyl-D-glucal was usefully converted to the jV-phenylsulfonyl D-glucosamine derivative, and the corresponding / -ethylt hio glycoside and /1-disaccharidcs, via an intermediate AT-sulfonylaziridine198. [Pg.806]

The recent addition of benzenesulfenyl chlorideto 3,4,6-tri-O-benzyl-D-glucal (76) resulted in practically complete gluco formation, providing easy access to the corresponding a-trichloroacedmidate (77 Scheme 26), which turned out to be an exceptionally reactive glycosyl donor, even though the com-... [Pg.60]

In some examples, the stereochemistry of radical reactions was controlled by chiral carbohydrate auxiliaries. As a radical counterpart to the ionic conjugate additions discussed above, Garner et al. [169] prepared carbohydrate linked radicals that were reacted with a,P-unsaturated esters. The radical precursor, the carboxylic acid 256, generated by the addition of ( Sj-methyl lactate to tri-O-benzyl-D-glucal and subsequent ester hydrolysis, was decarboxylated by Barton s procedure (Scheme 10.84) [170]. Trapping of the chiral radical 258 with methyl acrylate furnished the saturated ester 259 in 61% yield and with high diastereoselectivity (11 1). The auxiliary caused a preferential addition to the si-facQ of radical 258, probably due to entropic effects. The ester 259 was transformed in acceptable yield to the y-butyrolactone 261 by reductive removal of the thiopyridyl group followed by acid hydrolysis. [Pg.476]

The known dimerization reaction that takes place when glycals are treated with Lewis acids proceeded more efficiently with acetyl perchlorate (a known polymerization initiator of dihydropyran) in dichloromethane at —78 °C. For example tri-O-acetyl-D-galactal gave a 77 % yield of dimer 22. The report that tri-O-benzyl-D-glucal gives a cyclopentane derivative under these conditions has been corrected. ... [Pg.176]


See other pages where 3.4.6- Tri-O-benzyl-D-glucal is mentioned: [Pg.119]    [Pg.122]    [Pg.39]    [Pg.111]    [Pg.555]    [Pg.13]    [Pg.63]    [Pg.64]    [Pg.66]    [Pg.69]    [Pg.80]    [Pg.105]    [Pg.112]    [Pg.24]    [Pg.271]    [Pg.272]    [Pg.272]    [Pg.154]    [Pg.155]    [Pg.167]    [Pg.117]    [Pg.53]    [Pg.490]    [Pg.318]    [Pg.703]    [Pg.262]    [Pg.152]   
See also in sourсe #XX -- [ Pg.272 ]




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