Phosphoric acid esters, conformation

Cyclic Esters of Phosphorous Acid.—The conformational analysis of a number of 2-substituted-2-phospha-l,3-dithiacyclohexanes (121) and (122) has been carried out. The free energy for cis-trans equilibrium in (121) was determined, and although n.m.r. showed that the tertiary butyl group... 

Cyclic Esters of Phosphorous Acid.—A large number of 2-substituted-4-methyl-l,3,2-dioxaphospholans (88) have been prepared and their stereochemistry and conformations investigated by 1H and 31P n.m.r.69 Unlike the corresponding 1,3-dioxans, the tra/w-isomer (88a) is favoured in all cases, and each isomer is best described in terms of two rapidly equilibrating half-chair conformers with the 4-alkyl group pseudo-axial or pseudo-equatorial. 

Reactions of Phosphoric Acid and its Derivatives.—Theoretical studies on the conformational properties of cyclic and acyclic phosphate esters, including calculations of angle and torsional strain,66 and on the reactivity of monomeric metaphosphates,67 have appeared. 

Some food proteins are rich in phosphoric acid residues. The acid may either form ester bonds with Ser residues, as in caseins and egg proteins, or stabilize the native conformation of protein micelles by electrostatic interactions with negatively charged groups and calcium ions, as in caseins. In soy proteins Ser and Thr residues can be esterihed and Lys amidated with cyclic sodium trimetaphosphate at pH 11.5 and 35°C (Sung et al., 1983) ... 

Cyclic Esters of Phosphorous Acid.— Two groups have investigated the conformational preference of amino-substituents on phosphorus in 1,3,2-dioxaphosphorinans. Dipole moment and n.m.r. measurements show that... 

Bicyclic phosphites (297) undergo the Michaelis-Arbuzov reaction when treated with alky] halides at somewhat higher temperatures than required for the simple esters of phosphorous acid. The boat conformation which is undoubtedly an intermediate is presumably converted to the thermodynamically stable chair form. 

Employing nonempirical, ab initio calculations, these workers set out to explore the influence of conformation on the energy and electron distribution of ground-state, tetrahedral phosphoric acid—a simple model for phosphate esters in general. Calculations using a split sp basis set, with and without the addition of d-orbital functions, were carried out on three phosphoric acid conformers, mimicking monocyclic, acyclic and bicyclic phosphates. 

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