Methoxytrityl group

C, arc competitively deprotected at reflux. The more acid-sensitive di-methoxytrityl group cleaves faster and at lower temperatures than the trityl group. 

This group, used for 5 -phosphate protection, had hydrophobicity similar to the di-methoxytrityl group and thus was expected to assist in reverse phase HPLC purification of product from failure sequences in oligonucleotide synthesis. It is cleaved with BU4NF in DMSO at 70°C. ... 

Solid phase combinatorial synthesis is also applicable to purine nucleosides, as exemplified by the preparation of a library of more than five hundred 2,8-disubstituted guanosine analogues using SNAr displacement of the 2-fluoro group in the protected nucleoside 28, linked to the polystyrene resin with a methoxytrityl group through the ribose C-5 hydroxyl [54] (Scheme 12). The SnAt reactions were successful with primary or secondary alkylamines, but not with anilines or other arylamines. 

B. Cleavage of the 5 -0-di-/>-methoxytrityl group 3% (v/v) trichloro acetic acid in dichloromethane. 

Neither 0-p-methoxytrityl groups, which are readily cleaved by aq. acetic acid, nor / -cyanoethyl phosphate groups, which are sensitive to aq. NH3, are affected. F. e. s. R. L. Letsinger, P. S. Miller, and G. W. Grams, Tetrah. Let. 1968, 2621. 

In the 1,3,2-dioxaphosphole method a bis(2-butene-2,3-diyl) pyrophosphate is used as the condensing agent. It allows two successive esterifications of one phosphate group to be performed without additional activation. First a 5 -O-protected nucleoside is added in methylene chloride in the second reaction an unprotected nucleoside can be used, since only the 3 OH group is able to attack the cyclic enediol 3 -nucleosidyl phosphotriester. Protected dinucleoside triesters are obtained in 80% yield. Removals of protective groups, methoxytrityl by means of trifluoroacetic acid in methylene chloride and 1-methylacetonyl by aqueous triethyl-amine, also give about 80% yield (F. Ramirez, 1975, 1977). 

Massing described a synthesis of systematically modified cationic lipids by solid-phase chemistry starting with the immobihsation of (/f)-2,3-epoxy-1 -propanol on 4-methoxytrityl chloride resin [157], Reaction of the epoxide with distinct long-chained amines was followed by reductive animation and tertiary amine quatemisation (see Fig. lib). This interesting method allowed the solid-phase coupling of three different lipophUic moieties on an amino group and the synthesis... 

B. T. 4,4 -Dimethoxytrityl and 4,4, 4"-tri-methoxytrityl as protecting groups for amino functions selectivity for primary amino groups and application in 15N-labelling. 

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