E- or Z-selective Horner-Wittig reactions of substituted bicyclo[3.3.0]octane-3-ones with chiral phosphonoacetates

The Horner-Wittig reaction of substituted bicyclo[3.3.0]octane-3-ones with chiral phosphonoacetates 2 gave the corresponding unsaturated esters in $\text{E}$/$\text{Z}$-ratios of up to 91 : 9.     

Substituent effects on the gas phase basicities of acetophenones

The gas phase basicities of m- and p-substituted acetophenones have been determined by the ion cyclotron resonance (ICR) equilibrium constant method. The application of the LArSR Eq. to these substituent effects provides a ϱ=12.2 and an r⁺=0.76 with excellent precision.     

A synthesis of succinimides and glutarimides from cyclic anhydrides

The transformation of cyclic anhydrides to their corresponding imides involves a mild three-step sequence: (1) reaction with a primary amine, (2) conversion of the intermediate monoamide to an N-hydroxysuccinimidyl ester using N,N′-disuccinimidyl oxalate (DSO), and (3) cyclization by heating the NHS ester in trichloroethylene in the presence of 4-(dimethylamino)pyridine.     

Stereoselective synthesis and stereochemistry of altiloxin A

Stereoselective synthesis of (±)-altiloxin A not only confirmed the relative configuration but also opened the route providing the phytotoxin. Absolute configuration of (−)-altiloxin A was clarified by correlation with (−)−11-acetoxydriman-8-o1.     

Hydrolyse basique comparee d'esters allophaniques et phosphoriques en milieu mixte acetonitrile/eau faiblement aqueux; mise en evidence d'une entite catalytique,intermediaire de la reaction entre base et solvant

Kinetic study of base catalysed hydrolysis in acetonitrile-water Mixtures of allophanic esters (models of carboxybiotine) and phosphoric esters shows in the range of low water content (less than 1 molar) an enhancement in rate (10³) with a maximum at 0.1–0.3 molar in water. This rate enhancement is ascribed to ground state desolvation and the maximum is interpreted by a change in the rate determining step : leaving group departure in the tetrahedral intermediate is indeed the slow step for the reactions in acetonitrile/water mixture less than 0.1 molar in water. For charged phosphoric esters the rate enhancement from an aqueous medium (pH=10) to organic is larger since as high as 10⁶.On the other hand, in such a medium, an additional catalytic effect is observed; it is shown that it is due to the formation of a reactive species which results from reaction of the base on acetamide when accumulated in the medium from base catalysed hydrolysis of the solvent.     

Conformational study of the cembranolide diterpene denticulatolide by molecular mechanics method

The most stable conformation of denticulatolide (1), an ichthyotoxic cembranolide, obtained as a major metabolite of the soft coral, Lobophytum denticulatum, was given by molecular mechanics calculations and it was confirmed by ¹H NMR measurement. The geometry of 14-membered carbocycle of 1 was found to be different from that of derivative (2) especially around the juncture part of γ-lactone. The molecular mechanics calculation successfully reproduced the conformational changes between 1 and 2.     

Synthesis of allylic alcohols via organopalladium additions to unsaturated epoxides

The reaction of aryl- and vinylpalladium compounds with vinylic and allylic epoxides provides an excellent, high yielding, regio- and stereoselective route to functionally substituted allylic alcohols which can be made catalytic in palladium.