Benzyl idenation

Microwave-assisted epoxide ring-openings of l,5 2,3-dianhydro-4,6-0-benzyl-idene-D-allitol with nucleobases have been reported [218], Various rapid microwave-assisted protection and deprotection methods in the area of carbohydrate chemistry are known [210], and two general review articles on microwave-assisted carbohydrate chemistry were published in 2004 [219, 220]. 

Nitrene intermediates are implicated in the formation of the pyrrole (64) from an azirinyl aldehyde and (65).67 Treatment of the nitrosouracil (66) with benzyl idene-ylides affords the corresponding theophylline derivatives.68 Hydrazonic halides and keto-ylides initially give betaines (67), which ring-close to (68) on heating.69... 

Analogerhalt man aus (Benzylidenamino)-guanidin die entsprechenden 4-Aryl-2-(2-benzyl-iden-hydrazino)- bzw. 2-(2-Benzyliden-hydrazino)-4,5-diary 1-imidazole107,108 ... 

A novel method of opening of oxiranes involves the use of (chlo-romethylene)dimethyliminium chloride (39) [see Section II,2c p. 250], monochlorodeoxy or dichlorodideoxy derivatives are obtained, depending upon the reaction conditions employed.83 Thus, methyl 2,3-anhydro-4,6-0-benzylidene-a-D-allopyranoside (110) reacts with 39 in 1,1,2,2-tetrachloroethane at room temperature to give, upon hydrolysis of the primary adduct 111 with an aqueous solution of sodium hydrogen carbonate, methyl 4,6-0-benzylidene-2-chloro-2-deoxy-3-0-formyl-a-D-altropyranoside (112). If a solution of 39 and 110 in 1,1,2,2-tetrachloroethane is heated at reflux temperature, methyl 3,4-0-benzylidene-2,6-dichloro-2,6-dideoxy-o -D-altropyrano-side (113) is obtained in high yield the n.m.r. spectrum of 113, like that of 47 (see Section II, 2c p. 250), showed the presence of two diastereoisomers which differed in the configuration of the benzyl-idene-acetal carbon atom. 

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... 

Methyl 4,6-0-benzylidene-a-D-glucopyranoside Glucopyranoside, methyl 4,6-0-benzyl idene-a-D- a-D-glucopyranos1de, methyl 4,6-0-(phenylmethylene)- (3162-96-7), 65, 243... 

Vis and Karrer114 have found that treatment of methyl 4,6-O-benzyl-idene-2,3-O-p-tolylsulfonyl-a-D-glucoside (13) with lithium aluminum hydride provides methyl 4,6-0-benzylidene-3-deoxy-a-D-n 6o-hexoside (IS) in good yield. Since hydrogenolysis is possible at both C-2 and C-3 of the two possible 2,3-anhydro derivatives, only the alio isomer (14) could give the 3-deoxy derivative by further reaction with a reagent. Indeed, none of the alternative 2-deoxy derivative was found. This transformation is, un-... 

Detritylation Trityl ethers are cleaved by reaction with formic acid in ether in high yield in 7-45 minutes. Under these conditions isopropylidene and benzyl-idene acetals and r-butyldimethylsilyl ethers are not affected, but tetrahydropyranyl ethers are partially cleaved. 

N-[(a-Azidobenzylidene)-N -benzyl idene]-hydrazide. See under Benzalazine and Derivatives... 

In benzyl idene-t/Z-piperi tone, the two pairs of reactive double bonds that are related by a center of inversion are properly oriented for [2 + 2] photocycloaddition with 0 = 0°, 02 = 105.2°, 03 = 86.4°, and d = 3.93 A. However, there is no evidence for the presence of a dimer in the irradiated sample. The lattice energy... 

Analogues of 70 have been prepared by various methods including nucleophilic displacement of triflate esters attached directly to the oxetane ring (see Section 2.05.7.2) <2001TL4247>, from xylose, 145, via the benzyl-idene-protected oxetane, 146 (Scheme 24) <2004TA2667>, or from L-rhamnose, 147, via a l,4-lactone-2-O-triflate, 148 (and key oxetane 149 (Scheme 25)) <2004TA2681>. The /3-azidoester monomers formed by these methods were converted to the /3-amino acids and subsequently to /3-peptides by reduction of the azide and ester hydrolysis. 

A novel approach to chroman-6-ols involves a poor yielding photochemical benzannulation of the a- co-benzyl-idene-2-oxacyclohexylidene chromium complex 500 with alkynes (Equation 205) <1999SL231>. 

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