Rutaceous constituents—13: A biomimetic synthesis of acronycine

A biomimetic synthesis of the anti-tumor active alkaloid acronycine (7; R=R'=Me) has been obtained by cyclisationof 6-(2-methylaminobenzoyl)-5,7-dimethoxy-2.2-dimethylchromene (11 : R=R'=Me); isoacronycine (20; R=R'=Me) was also produced. In an analogous manner the aminochromene (11 ; R=H. R'=Me) gave a mixture of des-N-methylacronycinc (7; R=H, R$\text{=}\text{?}$Me) and des-N-methylisoacronycine (20; R=H, R'=Me). The aminochromenes were best synthesised by condensation of lithio-5,7-dimethoxy-2,2-irnethylchromene (22; R=Li) with N-methylisatoic anhydride (26) or with 2-methyl-3.1-benzoxazm-4-one (21).The relevance of this synthetic route to the biogenesis of acridone alkaloids is discussed.     

Singlet and triplet molecular interaction in excimers

A perturbative approach is developed to determine, term by term, the contributions of the various forces to the excimer potentials of the singlet and triplet excimers. The results show that the singlet excimer of naphthalene is more stable than the corresponding triplet excimer primarily due to large contributions of the exciton-resonance and the dispersion energy terms. The variation of the various terms with the conformations of the excimers suggests that the singlet and triplet excimers of naphthalene cannot have identical structure.     

Dielectric studies on sulphonated novolacs

The dielectric constants of novalac type of phenolic resins and their sulphonated derivatives were studied as a function of frequency, temperature and extent of sulphonation. The effect of moisture on the dielectric constant has also been reported. Introduction of —SO₃H groups into the polymer matrix increases the dielectric constant by several orders, while the resin continues to exhibit low losses.     

Facilitated transport in spherical shells: application of the combined damköhler number technique

In cell membranes, double emulsion drops, or other particles with spherical shell geometry, reversible carriers may be present which serve to facilitate transport of solutes into the particles. The physical phenomena taking place are both diffusion and chemical reaction. When the reaction deviates from chemical equilibrium, the solution of the conservation equations becomes difficult because the equations are non-linear. The combined Damköhler technique, recently devised by Hoofd and Kreuzer, is a simple analytical method to accurately predict facilitated mass transfer in the presence of non-equilibrium chemical reaction. The application of the combined Damköhler technique to spherical shell geometry gives accurate predictions of the facilitated flux over the full range of Damköhler numbers, when compared to results from a numerical analysis technique. The non-equilibrium facilitated flux depends on the sphericity of the spherical shell.     

Synthesis of spiropyrazolines

Synthesis of a series of novel 1,3,2′-triphenyl-4-aryl spiropyrazolines [5.4′]-2′-butenolides has been accomplished in good yield by regioselective 1,3-dipolar cycloaddition of diphenylnitrilimine with (E)-3-arylidenebutenolides. X-ray crystal structure analysis of one of the products 4a confirms the structure of the product and the regiochemistry of cycloaddition. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:517–522, 1998     

SOME INVESTIGATIONS ON POLY(SULPHUR OXIDE) AND ITS REACTION WITH SILICON TETRACHLORIDE

Abstract

Poly(sulphur oxide) has been prepared by the low temperature thermal decomposition of the lower oxides of sulphur. This yellow, elastic solid resists water hydrolysis. It is unstable at room temperature when stored under vacuum and decomposes slowly to a powdery yellow white cyclic(sulphur oxide) and sulphur dioxide. In the presence of silicon tetrachloride, the thermal decomposition gives rise to an adduct of the lower oxide of sulphur along with the poly(sulphur oxide). The adduct hydrolyses to silica, hydrogen chloride, hydrogen sulphide and hydrogen sulphite. Based on the analysis of the hydrolysed products and the IR data, the adduct is assigned a formula of SiCl₄·2(SO), in which the silicon is hexacoordinated.