Orthoformic acid derivatives cyclic

The condensation of 1,4-diamines with a variety of carboxylic acid derivatives, e.g. imidate esters, orthoformic esters, /V-ethoxycarbonylthioamides (77JOC2530), nitriles and ethoxyacetylene, produces the cyclic amidine linkage —N = C(R)NH— (67AHC(8)2l, p. 40). Cyclic ureas, —NHC(0)NH—, have been similarly produced using carbonyl chloride, A, A -carbonyldi imidazole, carbon monoxide, thiocarbonyl chloride or carbon disulfide (67AHC(8)21, p. 38). 

Triphenylacetic acid Ethylene derivatives from cyclic orthoformic acid esters... 

Upon treatment with (la), orthoformate (95) is converted into cyclic carbonate (96) by an allylic transposition [153]. This transformation is initiated by activation of the C-OMe bond of the orthoformate moiety (Scheme 9.64). The triol acid derived from (96) is a potent vasodilator. 

A variety of cyclic ortho esters,including cyclic orthoformates, have been developed to protect czs-1,2-diols. Cyclic ortho esters are more readily cleaved by acidic hydrolysis (e.g., by a phosphate buffer, pH 4.5-7.5, or by 0.005-0.05 M HCl) than are acetonides. Careful hydrolysis or reduction can be used to prepare selectively monoprotected diol derivatives. 

The cyclic anhydride was converted into the amide acid which on Hofmann rearrangement followed by lithium borohydride reduction on the ester gave a derivative of ip-amino-2a, 3a-dihydroxy-43-hydroxy-methylcyclopentane. Condensation of the amino-triol with 5-amino-4,6-dichloropyrimidine followed by ring closure with triethyl orthoformate gave the 6-chloropurine derivative which on treatment with ammonia gave 11. ... 

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