Triphenylmethyl group removal

The monothioacetal is also stable to 12 N hydrochloric acid in acetone (used to remove an TV-triphenylmethyl group) and to hydrazine hydrate in refluxing ethanol (used to cleave an A -phthaloyl group). It is cleaved by boron trifluoride etherate in acetic acid, silver nitrate in ethanol, and tiifluoroacetic acid. The monothioacetal is oxidized to a disulfide by thiocyanogen, (SCN)2- ... 

The triphenylmethyl group can be removed from the amine nitrogen under very mild conditions, either by catalytic hydrogenation or by hydrolysis in the presence of a weak acid ... 

Another putative approach to hexaphenylethane is to remove a spacer from between two triphenylmethyl groups, e.g. 

The helical conformation is lost when the triphenylmethyl group is removed from the polymer chain. Thus, the PMMA derived from the poly(TrMA) shows only a small optical activity based on the configurational chirality of the stereogenic centers in the vicinity of the chain terminals. ... 

The 2,4,6-trimethylbenzyl ester has been prepared from an amino acid and the benzyl chloride (Et3N, DMF, 25°, 12 h, 60-80% yield) it is cleaved by acidic hydrolysis (CF COOH, 25°, 60 min, 60-90% yield 2 N HBr/HOAc, 25°, 60 min, 80-95% yield) and by hydrogenolysis. It is stable to methanolic hydrogen chloride used to remove A-o-nitrophenylsulfenyl groups or triphenylmethyl esters. ... 

NO2C6H4SCI, AcOH (results in disulfide formation), followed by NaBH4 or HS(CH2)20H or dithioerythritol, quant." 5-Triphenylmethyl, 5-4,4 -di-methoxydiphenylmethyl, and 5-acetamidomethyl groups are also removed by this method. 

The triphenylmethyl function, also known as trytil (Trt), is a valuable bulky protecting group for peptide chemistry. Trytil groups confer acid-labile protection onto amines, but effective removal can also be achieved by catalytic hydrogenolysis. 

Benzyl and triphenylmethyl ethers of carbohydrates are preferred over methyl ethers when selective removal of protecting groups is important. The relatively high nucleophilic activity of the 5-hydroxyl group in glycosides and 1,2-O-alkylidene derivatives of 4 permits its benzylation and triphenylmethylation under mild conditions. Thus, treatment of 33 (Ref. 34) and 36 (Ref. 57) with benzyl bromide and... 

The constitution of the body formed by removal of the carbinol-chlorine from the halotriphenylmethyl chlorides can hardly be expressed by the formula (C 6H4Hlg)3C. Such a formula would indicate a similar function of the three phenyl groups which, in fact, does not exist. However, the same conclusion can now be drawn regarding triphenylmethyl itself also this hydrocarbon can hardly possess the simple formula (CgHsI C, however satisfactorily this symbol describes all other properties of this strongly unsaturated compound ... 

Amines can also be protected from unwanted acylation or from twofold alkylation by alkylation with a sterically demanding group that is amenable to selective removal after completion of the synthesis. The most commonly used groups for this purpose are triphenylmethyl derivatives. Amines are readily tritylated using trityl chloride in the presence of a tertiary amine. Deprotection is achieved by treatment with dilute... 

Triphenylmethyl (trityl) ethers of 2-amino-2-deoxy-D-glucose derivatives are formed with the primary C6-hydroxyl group, and they are useful intermediates in synthesis,6-166-178 being readily removed by hydrogen-olysis. 

Now we can strip away the protecting groups one by one and it is instructive to see how selective these methods are. The trityl group comes off in aqueous acetic acid by another SN1 reaction in which water captures the triphenylmethyl cation, and the benzyl group is removed by hydrogenoly-sis—hydrogen gas over a 10% palladium on charcoal catalyst in ethanol. 

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