O-Detritylation

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... 

O-Dealkylation s. Ethers, cleavage, O-Detritylation N-Deallylation 32, 997 Deamination... 

Selective O-detritylation. 6 moles of dicyclohexylcarbodiimide added to an anhydrous soln. of 5 -0-tritylthymidine and 2 moles of 2-cyanoethyl phosphate in pyridine, stored 2 days at room temp, in a well-stoppered flask, water added, after 1 hr. at room temp, coned, to dryness in vacuo, the residue... 

Sulfuric acid O-Aeyl group migration with O-detritylation... 

Trityl Ethers. Treatment of sucrose with four molar equivalents of chlorotriphenylmethyl chloride (trityl chloride) in pyridine gives, after acetylation and chromatography, 6,1, 6 -tri-O-tritylsucrose [35674-14-7] and 6,6 -di-O-tritylsucrose [35674-15-8] in 50 and 30% yield, respectively (16). Conventional acetylation of 6,1, 6 -tri-O-tritylsucrose, followed by detritylation and concomitant C-4 to C-6 acetyl migration using aqueous acetic acid, yields a pentaacetate, which on chlorination using thionyl chloride in pyridine and deacetylation produces 4,l, 6 -trichloro-4,l, 6 -trideoxygalactosucrose [56038-13-2] (sucralose), alow calorie sweetener (17). 

O-trityl-D-gaIactono-1,4-lactone (30c). Detritylation of 30c with F3B OEt2 caused 0-5 —> 0-6 acetyl migration, affording 30b, which was used for the preparation of 5-O-methyl-D-galactofuranose (39). 

As for the 2 - and 3 -ketouridines,2 both 2 - and 3 -ketocytidine derivatives have been found to be very unstable under basic conditions.25 Di-O-trityl-3 -, as well as 2 -, ketones 18a, 18c, 20a, and 20c, were completely degraded within 10 min at room temperature in 0.01 M methanolic sodium hydroxide, whereas the detritylated nucleosides 18b and 20b decomposed instantly under the same conditions. 

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