0,0,0-trichloroethyl group

The reactions of the p-D-glucopyranosides 5, and with TASF yielded results which were very different in each case, but which were fully consistent with the current understanding of nucleophilic displacements in carbohydrates (, —- ). The less rapid and efficient displacement of trlflate anion from as compared with that from may be attributable to the increased steric hlnderance occasioned by the Introduction of benzyl and 2,2,2-trichloroethyl groups in place of methyl groups. 

Chloral can also be reacted with urea to give 1-hydroxy-2,2,2-trichloro-ethyl urea [34, 35] and with other ureas (linear and cyclic) as well as sulfamides to give 1-hydroxy-2,2,2-trichloroethyl derivatives as described in references 34, 35. Other references to ureas containing the 2,2,2-trichloroethyl groups or flame retardants for polyurethanes should also be consulted [35,36, 37]. 

For conversion into the 2,3,4,2, 6 -pentapalmitoyl analog of 1-dephospho lipid A, compound requires only the debenzyl-ation of 0-1 and 0-3, and the cleavage of the trichloroethyl groups from the 4 -phosphate moiety. Work on the deprotection of this compound is in progress. 

The nucleotide derivatives (330, R = H, R = P032- and R = Me, R =P032-) were obtained analogously from (328) (R = H, Me) and the selectively protected nucleotide (331) [166, 167], The trichloroethyl groups were reductively cleaved with Zn-Cu couple, and saponification then gave the desired analogues. 

Variables in the production of tributyl phosphate have been discussed. In the presence of relatively large amounts (5—15 molar equivalents) ofcaesium fluoride or quaternary ammonium fluorides, 2,2,2-trichloroethyl phosphate esters readily trans-esterify with alcohols the sequential replacement of trichloroethyl groups becomes slower, so allowing the preparation of mixed (including cyclic) trialkyl phosphate esters, with the exception of those from t-butyl alcohol. ... 

Protection of primary hydroxyl groups. The 5 -hydroxyl groups of nucleosides can be protected as the a-naphthyldiphenylmethyl ether. The group is selectively cleaved reductively in the presence of a p-methoxytrityl protecting group by sodium anthracenide in THE (HMPT). Sodium naphthalenide is less selective. The a-naphthyldiphenylmethyl group is relatively stable toward the benzophenone radical anion, which readily cleaves /3,/3,/3-trichloroethyl groups. 

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