Trityl esters

Trityl esters have been cleaved by electrolytic reduction at —2.6 V. ... 

The trialkoxy benzhydrol linker, developed by Rink in 1987 [46] ( Rink acid resin , Figure 3.4) is a further acid-labile linker for carboxylic acids. Esters of this linker can, like trityl esters, be cleaved with acids as weak as acetic acid or HOBt [47], and care must be taken to avoid loss of the product during synthetic operations. 

Attachment of carboxylic acids to supports as trityl esters is achieved by treatment of the corresponding trityl chloride resin with the acid in the presence of an excess of a tertiary amine (Figure 3.5 see also Section 13.4.2). This esterification usually proceeds more quickly than the acylation of benzyl alcohol linkers. Less racemization is generally observed during the esterification of A-protected a-amino acids with trityl linkers than with benzyl alcohol linkers [47], If valuable acids are to be linked to insoluble supports, quantitative esterification can be accomplished by using excess 2-chlorotrityl chloride resin, followed by displacement of the remaining chloride with methanol [64]. 

Examples of the acylation of sterically demanding alcohols are given in Scheme 7.14. These reactions often proceed only slowly, and conditions suitable for most primary or secondary alcohols will fail with tertiary alcohols [46-48]. Trityl esters and similar compounds are difficult to prepare by acylation of the corresponding alcohols, but are readily accessible via O-alkylation of carboxylates. 

N- Trityl a-amino acids.1 TrBr is markedly superior to TrCl for tritylation of a-amino acids. The reaction of the acids with TrBr (2 equiv.) and (excess) triethyl-amine in CHC13/DMF (2 1) provides the N-tritylamino trityl ester, which is then hydrolyzed in situ with methanol at 50°. Yields are 80-86%. 

Synthesis of iV -Trt Amino Acids with Trt-Br via Intermediate Trityl Esters, General Procednre ... 

Trityl (triphenylmethyl, Trt) esters are extremely labile toward acidic conditions and are selectively cleaved in the presence of ferf-butyl esters by treatment with AcOH at room temperature for a few minutes.The hydrochloride salts of amino acid trityl esters are hydrolyzed in aqueous and methanolic solutions. Amino acid trityl esters are obtained in satisfactory yields by treatment of the corresponding N -protected amino acid cesium salts with trityl chloride.t l... 

The reported synthesis and properties of an oxaziridine by the thermal isomerization of the C7-trityl ester of 3-ac/nitrocamphor bears reinvestigation, particularly in view of the recent report that irradiation of nitronate salts yields hydrox-amic acids but that oxaziridine intermediates could not be detected.) A -Sulfonyl-oxaziridines also rearrange, thermally to nitrones that further decompose to products, but photochemically they yield amides. ... 

Trityl esters. Trityl bromide is regarded as superior to trityl chloride for the conversion of metal salts of acids into the trityl esters because it is more reactive and less hygroscopic and can be used with the dry silver, sodium, or potassium salt of the acid. Benzene usually serves satisfactorily as solvent. 

LiC104, toluene, 100°C, distillation to remove low boiling alcohol, 57-94% yield. Cinnamyl alcohols were prepared without Carrol rearrangement and a trityl ester was prepared, hut this most likely proceeds hy an alternative mechanism. ... 

Peptide synthesis. The reagent (1) is useful for solid-phase peptide synthesis as an acid-labile handle. A Fmoc amino acid may be derivatized as the trityl ester, thereafter the Fmoc group is removable by treatment with 40% piperidine-DMF without affecting the ester linkage. 

On the other hand, the copolymerization of (S)-a-nieth benzyl methacrylate (Ml) and trityl methacrylate(M2) by Buli in toluene yielded a mixture of an isotactic polytiBr of Ml and a less stereoregular copdymer, similady to the copdy-merization of methyl methacrylate(Mi) and trityl methacrylate(M2) in this solvent. If the (RS)-monomer was used instead of (S)-isomer, only the copdymer of low stereoregularity was produced, althou it had a wide distribution as to the composition. The low reactivity of trityl methacrylate in the copdymerization even with (RS)-o-methylbenzyl methacrylate may be also attributed to the sterk hindrance due to the bulkiness of the trityl ester, since the homopdymerization of this monomra itself proceeded extremely slowly in toluene. ... 

Carboxylic acid trityl esters from carboxylic acids via tbeir salts... 

Trityl esters s. Carboxylic acid trityl esters... 

One of the weak points of the PTrMA is the fact that the trityl ester is not strong enough and slowly solvolized in methanol, which is often used as the eluent in HPLC. The ability of the column gradually deteriorated and, therefore, it was requested that the methanol be completely replaced with hexane. The one-handed... 

The absolute stereochemistry of lyconesidine B (54) was elucidated by applying a modified Mosher s method (65) as follows. The hydroxy group at C-16 of 54 was protected with a triphenyl methyl (trityl) group and then esterified with its (S)- and (R)-MTPA chlorides, followed by hydrolysis of the trityl ester with formic acid to give its (S)- and (R)-MTPA esters. The values of AS [ (A-MTPA ester) - S(R-MTPA ester)]... 

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