Benzhydryl esters

Conceptually closely related, cefroxadi ne (40) can be prepared by several routes, including one in which the enol (33) is imethylated with diazomethane as a key step. A rather more involved route starts with comparatively readily available phenoxymethylpenicillin sulfoxide benzhydryl ester (36). This undergoes fragmentation when treated with benzothiazole-2-thiol to give Ozonolysis (reductive work-up) cleaves the... 

Another way for the synthesis of cefoxitin is started from 7-aminocephalosporanic acid, more correct, from its benzhydryl ester (32.1.2.31), which is synthesized by previous tosylation of the amino group of the initial 7-aminocephalosporanic acid, esterification of the carboxyl group by diphenyldiazomethane, and subsequent removal of the tosyl protection. 

In the tricyclic inhibitor series amidation of benzhydryl ester 81b with phenyllactic acid or mono-ferf-butyl /i-benzylsuccinate gives 395 (92EPP481522) and 396 (95USP5455242), respectively. A similar amidation... 

The indirect electrochemical deblocking of benzylic esters by tria,rylamine cation radicals differentiates not only between unsubstituted benzyl esters and 4-methoxy-benzyl, 2,4-dimethoxybenzyl, or benzhydryl esters, but, contrary to common methods, also between the acid-labile 2,4-dimethoxybenzyl esters and the likewise acid-labile 4-methoxybenzyl and benzhydryl esters The jV-(f-butoxycarbonyl)... 

This then collapses, possibly by way of the benzhydryl-carboxylate ion-pair, to the benzhydryl ester. Since, however, it is clear that ester formation plays no part in the slow step of these reactions, they will not be discussed in detail here. 

Dim en hydrin a te. Dimenhydrinate [523-87-5] (Dram amine) (18) is a white crystalline, ododess powder that melts between 102 and 107°C. It is sparingly soluble in water, freely soluble in ethanol and chloroform, and sparingly soluble in diethyl ether. Dimenhydrinate is prepared by combining dimethylaminoethyl benzhydryl ester with 8-chlorotheophylline and refluxing in an isopropyl alcohol solution. The crystalline precipitate of dimenhydrinate that forms on cooling is collected by filtration, washed with cold ethyl acetate, and dried. 

Diphenylmethyl (benzhydryl) esters.3 These esters can be cleaved either by acid hydrolysis or hydrogenolysis. They have been prepared by reaction of carboxylic acids with diphenyldiazomethane, generated in situ by oxidation of ben-... 

C s -lodomethylcephalosporins. C3-Acetoxymethyl- or C3-carbamoylmethylce-phalosporins (1) are converted to C3-iodomethylcephalosporins (2) on reaction with lSi(CH3)3 in CH2C12 at 20°. The ester group in 1 is not cleaved if it is benzyl or t-butyl, but p-methoxybenzyl or benzhydryl esters are cleaved faster than the allylic acetate group. This reaction is observed with both A2- and A3-cephems.5... 

Oxo-7-phenylacetylamino-5-thia-l-aza-bicyclo[4.2.0]oct-l-ene-2-carboxylic acid benzhydryl ester Phosphorus pentachloride/pyridine reagent... 

The 8-oxo-7-phenylacetylamino-5-thia-l-aza-bicyclo[4.2.0]oct-l-ene-2-carboxylic acid benzhydryl ester is reacted with phosphorus pentachloride/pyridine reagent in methylene dichloride, and the reaction mixture is thereafter cooled to -35°C and treated with methanol to produce hydrochloride of 7-amino-8-oxo-5-thia-l-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester. This hydrochloride is reacted with 4-(3-aminothiophen-2-yl)-5-oxohex-3-enoic acid 3-methylbut-2-enyl ester. Then 7-[2-(2-benzoylamino-thiazol-5-yl)(3-tert-butyl-4,4-dimethylpent-2-enoxycarbonyl)-pent-2-enoylamino]-8-oxo-5-thia-l-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid synthesized is reacted with aluminum chloride in anisole and diluted hydrochloric acid and then with dimethylmalonate to give 5-thia-l-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid, 7-(((2Z)-2-(2-amino-4-thiazolyl)-4-carboxy-l-oxo-2-butenyl)amino)-8-oxo-, (6R,7R)- (Ceftibuten). 

S-[2 -tert-butoxycarbonyl-amino-1 (S)-(2-thienyl)ethyl]-N-phthaloyl-L-cysteine benzhydryl ester (Q)... 

SYNS AMBENYL BAX BENA BENADRYL BENDYLATE BENOCTEN BENZEHIST BENZ-HYDRAMINE HYDROCHLORIDE 2-(BENZHYDRYL-OXY)-N>l-DLMETHYLETHYL-AMINEHYDRO-CHLORIDE DABYLEN DIFENHYDRAMINE HYDROCHLORIDE DIMETHYLAMINE BENZHYDRYL ESTER HYDROCHLORIDE p-DIMETHYLAMINOETHYL BENZHYDRYL ESTER HYDROCHLORIDE DIPHENYLHYDRAMINE HYDROCHLORIDE 2-piPHENYLMETHOXY)-N,N-DIMETHYL-ETHANAMINE HYDROCHLORIDE 02-DIPHENYLMETHOXY-NJSI-DIMETHYLETHYLAMINE HYDROCHLORIDE DOLESTAN ELDADRYL FELBEN FENYLHIST HALBMOND O-HYDR-... 

Much kinetic work has been done on the reaction of diphenyldiazo-methane with weak acids, HA (mainly carboxylic acids), in ethanol or toluene solutions [214, 216]. In these studies, catalysis by solvated protons is negligible in ethanol and non-existent in toluene. The reaction is first-order in diphenyldiazomethane and first-order in weak acid, HA. Reaction products in ethanol are benzhydryl ethyl ether (Ph2 CHOEt) and benzhydryl ester (Ph2 CHA). The only product in toluene is benzhydryl ester. The product ratio of the reaction in ethanol is insensitive to the addition of salts of the weak acid, and it is almost independent of the chemical nature of HA [216]. The solvent isotope effect in the reaction with benzoic acid in ethanol is (fenAktoH/ Da)eiod = 3.5. 

Fluorenyl esters have been recommended as a useful alternative to the benzhydryl (diphenylmethyl) esters in the protection of amino acids.P l They are readily prepared from 9-diazofluorene and the amino acid following a similar procedure to that for the benzhydryl esters. Cleavage is accomplished by mild acidolysis or hydrogenolysis. 

The Fraction of Benzhydryl Ester, R, in the Products of Reaction of DDM with Acids at 30°... 

The reaction of DDM with carboxylic acids has been studied in toluene (More O Ferrall et al., 1964). The product is almost exclusively the benzhydryl ester of the acid. The kinetics of the reaction are accurately... 

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