Trityl derivative

Triphenylmethyl chloride, (C6H5)3C—Cl, was shown by Helferich and associates (34) to react with sugars, glycosides, and derivatives to form the triphenylmethyl ethers, commonly called trityl derivatives. The reagent exhibits a marked difference in the rate of reactivity for the primary 

Rate of Reaction op Sugar Derivatives with Trityl Chloride 

Under more prolonged treatment, or at elevated temperatures, secondary alcoholic groups also react certain of the methyl pentopyranosides and 6-deoxyhexosides, which contain no primary hydroxyls, have been found to give mono- and ditrityl derivatives ( 5) D-ribose, when tritylated at 100°, gives a tritrityl derivative ( 6). 

The rates of reaction of triphenylmethyl chloride with several characteristic compounds are given ( 7) in Table I, which also illustrates the effect of the trityl chloride concentration. For the 8-fold excess, the primary alcoholic group of the galactose derivative reacts 226 times as rapidly as the secondary alcoholic group of the glucose derivative. However, the difference between the primary alcoholic group of the sorbose derivative and the secondary hydroxyl of the glucose derivative is only 34 times. 

This kinetic comparison is made between primary hydroxyl groups and 

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In practice the various trityl derivatives are cleaved with acid, but the monomethoxy derivative can be cleaved with sodium naphthalenide in HMPA (90% yield).It is not cleaved by sodium anthracenide, used to cleave a-naphthyldi-phenylmethyl ethers. 

MeNSO and 120° in HNSO, cf. 119° in SO2. The trityl derivative PhsCNSO is the only alkyl derivative to have been structurally characterized in the solid state. 

The unusual formation of an anhydro sugar by the hydrolysis of a trityl derivative has been described.76 The treatment of 5-trityl-D-ribofuranose triacetate with hydrogen bromide in acetic acid gives a ribosan diacetate which is presumed to be 1,5-anhydro-D-ribofuranose diacetate. 

The two primary hydroxyl groups in maltose and its derivatives show a large difference in reactivity. On selective tritylation, /3-maltose,238 benzyl /3-maltoside,239 and methyl 3-0-(methylsulfonyl)-/3-maltoside127 all gave mainly 6 -0-trityl compounds. Tritylation of cyclohexaamylose130 and amylose132,240 yielded the expected 6-0-trityl derivatives. 

The SPSS following this route is illustrated in Scheme 5. In the first step, Fmoc-protected glycine is attached to a trityl-derived hydroxyl... 

Serine esters can be O-alkylated without concomitant A -alkylation, when the amino group is protected as its trityl derivative. The reaction is generally high yielding under relatively mild conditions [33], particularly with the more reactive allyl and benzyl halides. 

Recently the tetrazole moiety has attracted interest as a useful directing group for the lithiation of 5-aryl substituents, with the dianion derivative 62 being obtained in the case of the unsubstituted parent compound and the monolithio species 63 in the case of the 2-trityl derivative (91TL6857 91USP50398I4). With both systems, good yields of products were obtained after reaction with a variety of electrophiles. 

The method of Horton and coworkers,123 just mentioned, for bro-mination in methanol in the presence of silver acetate, has also been applied to the 2,3-dideoxy-6-0-trityl-o -D-erythro-hex-2-enopyrano-glycan derived from a 2,3-di-0-p-tolylsulfonyl-6-0-trityl derivative of amylose a 2,3-dibromide having a degree of substitution of approximately 2.0 was obtained.124... 

O-Tritylation.2 A trimeihylsilylated alcohol, phenol, or carboxylic acid can be converted into the corresponding trityl derivative by reaction with I catalyzed by trimethylsilyl inflate (equation I). r-Butoxytrimethylsilane can be used, but it is less effective. 

Other Acylglycerols. If some of the DGs in freshly drawn milk are involved in biosynthesis, it is possible that they are enantiomeric and are probably the sn-1,2 isomer. If so, the constituent fatty acids are long chain. Their configuration can be determined by stereospecific or other analyses, but it is difficult to accumulate enough material for analysis. Nevertheless, Lok (1979) isolated the DGs from freshly extracted cream as the trityl derivatives. Trityl chloride reacts selectively with primary hydroxyls. The stereochemical configuration of the DGs was identified as sn-1,2 therefore, these residual DGs were most likely intermediates of biosynthesis. If the DGs were products of lipol-ysis, they would be a mixture of 1,2/2,3 isomers in a ratio of about 1 2, since milk lipoprotein lipase preferentially attacks the sn-1 position of TGs (Jensen et al. 1983). 

Finally, isosorbide was tritylated to afford both of the monotrityl isomers, which were separated chromatographically. The 2-O-trityl derivative 97 was then used for the preparation of isosorbide 5-nitrate (11) by way of intermediate152 98 (see Scheme 21). Earlier reports on both of the 2,5-di-O-trityl... 

Detritylation (10, 461).5 A detailed study of detritylation of nucleotide derivatives with ZnBr2 in CH2Cl2-2-propanol indicates that recombination to the trityl derivative can occur on neutralization. This reaction can be decreased by use of a large excess of ZnBr2 and by neutralization of ZnBr2 by addition of 4-f-butylpyridine, which forms a complex with ZnBr2 (m.p. 205-210") that precipitates on addition of CH3OH. 

Unsubstituted tetrazolyl derivative 458 was also prepared according to the following procedure (91MIP2). A solution of 5-phenyl-2-trityltetrazole in tetrahydrofuran was first treated with 1.7 M ferf-butyllithium in pentane at -25°C, in two parts. After about 30 minutes, an organolithium salt precipitated. Then a 1 M ethereal solution of zinc chloride was added to the mixture, which was then warmed to room temperature. Bis(triphenyl-phosphine)palladium(Il) chloride and 4//-pyrido[l,2-a]pyrimidin-4-one 457 were added to the reaction mixture, and after boiling for 4 hours, the 2-trityl derivative of 458 was obtained in 56% yield. Finally, detritylation with a mixture of methanol and concentrated hydrochloric acid yielded tetrazole derivative 458. 

Problems may appear in the chromatographic purification of trityl ethers depending on the type and activity of the sorbent, the silica gel-catalyzed detritylation has been observed [256-259]. In 1962, Buchanan and Schwarz found it necessary to pre-treate with ammonium hydroxide the silica gel used for the chromatographic purification of trityl derivatives [258],... 

Tritylation of sucrose has been explored intensively [277-282] to show the low reactivity of the primary hydroxyl group at C-l of the p-D-fructofuranosyl moiety. Monotritylation of raffinose afforded the 6 -trityl and 6"-trityl ethers in 1.7 and 9.4% yields [283], whereas the 1, 6, 6"-tri-0-trityl derivative was the major product (20%) of the trimolar tritylation [284],... 

Just as in the case of nucleosides, the older results were re-investigated with novel methods also for tritylation of pyranosides. All the monotrityl ethers of methyl p-D-xylopyranoside and methyl oc-D-xylopyranoside have been isolated recently [311] to complement the pioneering work by Hockett and Hudson [312], The monotrityl fraction obtained [313] from methyl a-L-fucopyranoside was now found [314] to consist of 2-0- and 3-0-trityl derivatives in the ratio of 3 2 (D-enantiomer has been actually studied). 

Selective tritylation of methyl oc-L-rhamnopyranoside yielded 57% of the 3-0-trityl derivative, together with 1 % of the 2-0- and 3 % of 4-0-trityl isomers. For methyl P-L-rhamnopyranoside, 34% of the 3-trityl and 17% of the 4-trityl ether were obtained [315]. Similarly, the 3,6-ditrityl ether is the major product of ditrityl-ation of methyl and benzyl a-D-mannopyranosides [316]. The corresponding a-D-glucopyranosides yielded the 2,6-di-O-trityl derivative, whereas both the 2,6- and 3,6-ditrityl ethers were isolated in the case of [Pg.237]

The introduction of methoxy substituents increases the ease of removal of trityl groups under acid conditions, but also decreases the selectivity for the primary hydroxyl group [377]. As a compromise, the monomethoxytrityl and dimethoxy-trityl groups found widespread use for the protection of primary positions of glycosides (see, e.g. Ref. [378]) and, especially for the OH-5 function of nucleosides [377]. The use of 6-nitroquinoline instead of pyridine was described [379] to improve the selectivity of monomethoxytritylation of nucleosides and nucleotides bearing free amino groups. A general and rapid procedure was developed for the preparation and isolation of 5 -0-dimethoxy trityl derivatives [380]. 

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