Methyl 3,4-0-benzylidene 2-deoxy-2-iodo

The stereoselective introduction of an ethynyl group in various flve- and six-membered iodohydrins has also been developed by the same group (O Scheme 37) [60]. Treatment of 3 -ethynyldimethylsilyl 2-deoxy-2-iodo-D-mannopyranoside 142 with Et3B and TBAF in toluene furnished the methyl 2-deoxy-2-C-ethynyl-4,6-0-benzylidene-a-D-mannopyranoside 144 in 85% yield. However, a similar reaction of 3-iodo-D-ribosyl substrate 143 having the [2-(trimethylsilyl) ethynyl]dimethylsilyl at C-5 gave the desired product 5-0-acetyl-3-deoxy-3-C-ethynyl-l,2-0-(l-methyl ethylidene)-a -D-xylofuranose, in which the ethynyl group was introduced at the y-cis position to the 5 -hydroxyl, in only 31% yield. This may be explained by an unfavored 6-exo radical cyclization. 

Methyl 3-acetamido-2,5-di-0-acetyl-3-deoxy-a-D-ribofuranoside, A-330 Methyl 3-acetamido-2,5-di-0-acetyl-3-deoxy-p-D-ribofuranoside, A-330 Methyl 3-acetamido-2,4-di-0-acetyl-3-deoxy-a-D-ribopyranoside, A-330 Methyl 5-amino-5-deoxy-2,3-0-isopropylidene-p-D-ribofuranoside, A-332 Methyl 3-amino-3-deoxy-p-D-ribofuranoside, SCI, A-330 Methyl 5-0-benzoyl-2,3-0-benzylidene-p-D-ribofuranoside, M-208 Methyl 5-0-benzoyl-2,3-di-0-tosyl-p-D-ribofuranoside, M-208 Methyl 5-0-benzoyl-2,3-0-methylene-p-D-ribofuranoside, M-208 Methyl 2,3-0-benzylidene-5-deoxy-5-iodo-p-D-ribofuranoside, D-272 Methyl 5-bromo-5-deoxy-2,3-0-isopropylidene-a-D-ribofuranoside, B-93 Methyl 5-bromo-5-deoxy-2,3-0-isopropylidene-p-D-ribofuranoside, B-93 Methyl 5-bromo-5-deoxy-2,3-0-isopropylidene-p-L-ribofuranoside, B-93 Methyl 5-bromo-5-deoxy-2,3-0-isopropylidene-p-DL-ribofuranoside, B-93 Methyl 5-chloro-5-deoxy-2,3-0-isopropylidene-p-D-ribofuranoside, C-100 Methyl 5-chloro-5-deoxy-a-D-ribofuranoside, C-100 Methyl 5-chloro-5-deoxy-p-D-ribofuranoside, C-100 Methyl 5-deoxy-5-iodo-2,3-0-isopropylidene-p-D-ribofuranoside, D-272 Methyl 5-deoxy-2,3-0-isopropylidene-p-D-ribofuranoside, D-362 Methyl 5-deoxy-D-ribofuranoside, D-362... 

Methyl 4,6-O-benzylidene-3-0-tosyl-a-D-mannopyranoside, M-169 Methyl 5-0-benzyl-2,3-0-isopropylidene-a-D-mannofiiranoside, 1-71 Methyl 6-6 -benzyl-2,3-0-isopropylidene-a-D-mannofiiranoside, 1-71 Methyl 2,6-0-benzyl-3-0-methyl-a-D-mannopyranoside, M-271 Methyl 4-0-benzyl-6-0-trityl-a-D-mannopyranoside, M-215 Methyl 2-bromo-2-deoxy-a-D-mannopyranoside, B-87 Methyl 2-bromo-2-deoxy-p-D-mannopyranoside, B-87 Methyl 6-deoxy-6-iodo-2,3-di-0-mesyl-a-D-mannopyranoside, D-266 Methyl 6-deoxy-6-iodo-2,3-0 -isopropylidene-a-D-mannopyranoside, D-266... 

Methyl 6-deoxy-6-iodo-a-D-mannopyranoside, D-266 Methyl 6-deoxy-6-iodo-p-D-mannopyranoside, D-266 Methyl 2,3-diacetamido-4,6-0-benzylidene-2,3-dideoxy-a-D-mannopyranoside, D-449... 

Methyl 2,3-anhydro-4,6-0-benzylidene-a-D-taIopyranoside, A-70S Methyl 2,3-anhydro-4,6-0-benzylidene-p-D-taIopyranoside, A-708 Methyl 2,6-anhydro-3,4-di-0-methyl-p-D-talopyranoside, A-710 Methyl 2,6-anhydro-3,4-0-isopropylidene-a-D-talopyranoside, A-710 Methyl 2,6-anhydro-3,4-0-isopropylidene-p-i>talopyranoside, A-710 Methyl 2,6-anhydro-a-D-talopyranoside, A-710 Methyl 2,6-anhydro-P-D-talopyranoside, A-710 Methyl 4-bromo-4-deoxy-a-D-taIopyranoside, B-97 Methyl 4-bromo-4-deoxy-6-0-trityl-a-i>talopyranoside, B-97 Methyl 2-deoxy-2-iodo-a-D-talopyranoside, D-275... 

The reaction of 39 with methyl 4,6-0-benzylidene-2-deoxy-2-iodo-a-D-altropyranoside (48) gave a complex mixture of products, from which methyl 4,6-0-benzylidene-2,3-dideoxy-a-D-eryf/iro-hex-2-eno-pyranoside (50) could be isolated. The formation of 50 was ex-plained83(b) by attack by chloride ion on the iodine atom in intermediate 49, followed by elimination of the substituent at C-3. Compound 50 itself reacts with reagent 39, and, therefore, prolonged reaction times led to extensive decomposition. 

A branched-chain iodo sugar derivative, l,5-anhydro-4,6-0-benzyl-idene-2,3-dideoxy-3-C-(iodomethyl)-D-rifoo-hex-l-enitol [4,6-O-ben-zylidene-3-deoxy-3-C-(iodomethyl)-D-allal] (200), is one of the products formed on treatment of methyl 4,6-0-benzylidene-2,3-dideoxy-a-D-en/thro-hex-2-enopyranoside (77) with the Simmons-Smith reagent (diiodomethane and zinc-copper couple).123,212 Compound 200 displays high solvolytic reactivity, an observation that has been rationalized by supposing the formation of the highly stabilized carbonium ion213 (201). Thus, under conditions wherein methyl 2,3,4-tri-0-acetyl-6-deoxy-6-iodo-a-D-glucopyranoside required more than 24 hours to react appreciably with an excess of silver nitrate in 50% aqueous p-dioxane buffered with silver carbonate, the iodide 200 was hydrolyzed completely in less than 1 minute the product of hydrolysis of 200 is the cyclopropyl aldehyde 202. Methanolysis of... 

Treatment of methyl 4,6-0-benzylidene-2-benzyloxycarbonylamino-2-deoxy-3-0-(imidazole-l-sulfonyl)-a-D-glucopyranoside with tetrabutylammonium iodide in refluxing toluene (3 h) gave the corresponding iodo derivative in 90% yield [68] (Scheme 13). When... 

For the synthesis of the D-C portion, two different concepts were followed either by modification of laminaribiose (166) [89] or by a stereospecific P, 1 ->3-glycosylation [20]. Laminaran is isolated from seaweeds or from Poria cocos Wolf, degraded by selective acetolysis, and the lower oligomers separated by preparative HPLC [90]. Following acetylation, the heptaacetyl laminaribiosyl bromide is prepared and transformed into the disaccharide glycal 167 by the classical approach in 93 % yield. The 2-deoxy-2-iodo-a-glycoside is formed by application of the NIS procedure after deprotection and subsequent 4,6-0-benzylidenation, the precursor 168 for the radical formation of the 6,6 -dibromo-6,6 -dideoxy derivative is at hand. This compound may be further reduced to methyl-3-0-(P-D-chinovosyl)-a-D-olivoside (169). 

When a p-tolylsulfonyloxy group is adjacent and trans to an iodine atom, both groups are eliminated by the action of sodium iodide in acetone, to give an unsaturated sugar. Newth has shown that methyl 4,6-0-benzylidene-3-deoxy-3-iodo-2-0-p-tolylsulfonyl-a -D-glucopyranoside gives... 

The reaction of epoxides of carbohydrates with methylmagnesium iodide gives mainly deoxyiodo alcohols which, on p-toluenesulfonylation, afford derivatives []for example, methyl 4,6-0-benzylidene-3-deoxy-3-iodo-2-0-p-tolylsulfonyl-a-D-glucoside (74), prepared from methyl 2,3-anhydro-4,6-0-benzylidene-at-D-allopyranoside ] which imdergo ready elimination when treated with sodium iodide in acetone (Route A). The general applicability of this route to unsaturated compounds has been noted, and, in the pentose series, it has been applied to the preparation of methyl 4-0-benzyl-2,3-dideoxy- 3-L-glj/cero-pent-2-enoside (79). Here, the elimination occurs much... 

Me glycoside, 3,4-O-benzylidene fR-J. Methyl 3,4-0-(K)-benzylidene-2-deoxy-2-iodo-a-D-altropyranoside [35775-00-9]... 

Me glycoside, 4,6-O-benzylidene, 3-Ac Methyl 3-0-acetyl-4,6-O-benzylidene-2-deoxy-2-iodo-fS-D-altropyranoside [18968-74-6]... 

Me glycoside, 4,6-O-benzylidene, 2-tosyl Methyl 4,6-0-benzylidene-3-deoxy-3-iodo-2-0-tosyl-a-D-altropyranoside C2tH23l07S 546.379 Cryst. (EtOH). Mp 128-129°. [ag +46.4 (CHCI3) (+37.5). Unstable at r.t., dec. to a dark tar. 

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