Detritylation selective

Dess-Martin periodinane s. 1,2-Ben-ziodoxol-3-one, 1,1,1-triacetoxy-N-Detritylation, selective 43, 30 a-Deuteriocarboxylic acids... 

N-Detosylation s. a. Amines from sulfonic acid amides —, preferential 16, 367 0-Detritylation, selective 16, 3 Deuteriation 16, 694... 

Detritylation. Diethylaluminum chloride or diisobutylaluminum c hloride effects selective quantitative removal of trityl groups of deoxynucleosides, deoxynucleotides, or oligodeoxynucleotides in methylene chloride at 25° in 2-10 minutes.12... 

Selective N-deacylation.x N,0-Peracylated nucleotides are converted to the 0,0-diacylated nucleotides by treatment with zinc bromide in chloroform and either methanol or ethanol (CHCl3/alcohol = 1 4 v/v). Higher alcohols are less effective. However, the mixed solvent CH2Cl2-(ClI3)2CHOH (85 15 v/v) is recommended for detritylation with ZnBr2. 

Selective O-tritylation of a primary hydroxyl group of L-arabinose diethyl dithio-acetal (116) with trityl chloride and 4-dimethylaminopyridine (DMAP), successive benzylation with benzyl bromide, and O-detritylation with p-toluenesulfonic acid, followed by tosylation gave 2,3,4-tri-0-benzyl-5-0-tosyl-L-arabinose diethyl dithio-acetal (777), [a]J,8 —2° (chloCEoform). Cleavage of the diethyl dithioacetal group with... 

Trityl ethers are easily cleaved by mild pro tic acids such as aqueous acetic or trifluoroacetic acid owing to the stability of the triphenylmethyl carbocation. They are also labile in the presence of Lewis acids such as ZnBr2—MeOH, FeCl3 or BF3 Et20.2 Trityl ethers can be cleaved selectively in the presence of TBDMS ether and isopropylidene acetals by brief exposure to formic acid.22 Catalytic hydrogenation has also been used to effect (9-detritylation. 

Experimental protocols for selective detritylation of peptides containing Cys(Trt) are reported in Section 2.6.6.2.I.3.3. 

So far, no detailed synthetic procedure has been reported for the most commonly used derivative, Fmoc-Tyr(Trt)-OH.t l Due to the increased acid sensitivity, some modifications to the procedure for the preparation of Fmoc-Ser(Trt)-OH (see Section 2.6.4.1.1.3, Table 4) have to be performed. The mixture comprising the intermediates Trt-Tyr(Trt)-OH and Trt-Tyr(Trt)-OTrt, obtained on treatment of Trt-Tyr-OH TEA with trityl chloride, can be selectively detritylated at the amino and carboxy groups by the addition of ACOH/TFE/CH2CI2 (1 2 7) or with HOBt in TFE/CH2CI2 (1 3) at 0°C. No information concerning reaction time, HOBt amount, or workup procedures was reported. 

The key compound on the way to the debranched nagstatin 175 has been synthesized from the L-ribose derivative 176 by employing ring-chain interconversion involving addition of trityl imidazole, selective sulfonylation, and warm acetylation which causes detritylation with cyclization [139] (O Scheme 42). 

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