Synthesis of (9E)-isoambrettolide, a macrocyclic musk compound, using the effective lactonization promoted by symmetric benzoic anhydrides with basic catalysts

Two alternative methods for the synthesis of (9E)-isoambrettolide are established via the rapid lactonization of the free threo-aleuritic acid or its protected seco-acid using substituted benzoic anhydrides with basic catalysts. The most efficient lactonization of the threo-aleuritic acid is performed using 2-methyl-6-nitrobenzoic anhydride (MNBA) with a catalytic amount of 4-dimethylaminopyridine N-oxide (DMAPO).     

Bifunctional-thiourea-catalyzed diastereo- and enantioselective aza-Henry reaction

Bifunctional thiourea 1a catalyzes aza-Henry reaction of nitroalkanes with N-Boc-imines to give syn-beta-nitroamines with good to high diastereo- and enantioselectivity. Apart from the catalyst, the reaction requires no additional reagents such as a Lewis acid or a Lewis base. The N-protecting groups of the imines have a determining effect on the chirality of the products, that is, the reaction of N-Boc-imines gives R adducts as major products, whereas the same reaction of N-phosphonoylimines furnishes the corresponding S adducts. Various types of nitroalkanes bearing aryl, alcohol, ether, and ester groups can be used as nucleophiles, providing access to a wide range of useful chiral building blocks in good yield and high enantiomeric excess. Synthetic versatility of the addition products is demonstrated by the transformation to chiral piperidine derivatives such as CP-99,994.     

A three-component approach to isoquinoline derivatives by cycloaddition/Heck reaction sequence

Here, we report a three-component coupling reaction approach between an aldehyde, an allyloxyamine, and a maleimide toward isoquinoline derivatives. At first, an oxime O-allylic ether, prepared by dehydrative condensation of the aldehyde and the allyloxyamine, was reacted with the maleimide in the presence of a Pd²⁺ species. The cycloadduct obtained was then subjected to the Heck cyclization employing a Pd⁰ species to give thermodynamically stable diastereomer of isoquinoline derivatives selectively in 25-78% yields.     

An effective use of benzoic anhydride and its derivatives for the synthesis of carboxylic esters and lactones: a powerful and convenient mixed anhydride method promoted by basic catalysts

Various carboxylic esters are obtained at room temperature in excellent yields with high chemoselectivities from nearly equimolar amounts of carboxylic acids and alcohols using 2-methyl-6-nitrobenzoic anhydride with triethylamine by the promotion of a basic catalyst such as 4-(dimethylamino)pyridine. A variety of lactones are also prepared in high yields at room temperature from the corresponding omega-hydroxycarboxylic acids with use of 2-methyl-6-nitrobenzoic anhydride in the presence of 4-(dimethylamino)pyridine. A similar reaction occurs with triethylamine when using a catalytic amount of 4-(dimethylamino)pyridine 1-oxide as an effective promoter for the intramolecular condensation reaction. These methods are successfully applied to the synthesis of erythro-aleuritic acid lactone and an eight-membered-ring lactone moiety of octalactins A and B. The efficiency of the cyclizations is compared to those of other reported lactonizations.     

Enantioselective aza-Henry reaction catalyzed by a bifunctional organocatalyst

[reaction: see text] The aza-Henry reaction of imines with nitroalkanes was promoted by chiral thiourea with an N,N-dimethylamino group to give beta-nitroamines with good enantioselectivity. Various N-protected imines were examined as substrates. N-Phosphinoylimine gave the best result in terms of chemical yield and enantioselectivity (up to 91% yield, up to 76% ee).     

Fabrication of potassium tantalate films by hydrothermal electrochemical method at low temperature

Potassium tantalate was formed to pyrochlore structures on the tantalum substrate by hydrothermal or electrochemical method. In synthesizing process of potassium tantalate, a crystal structure of the substrate surface seemed to be an important factor. Potassium tantalate was synthesized with a simple equipment only, low temperature of 323 K or over, low concentration of 2–4 mol per liter potassium hydroxide aqueous solution and short time.     

Thermal behaviour and S-O bonding state of alkaline-earth metal sulfites

The thermal behaviours of magnesium sulfite, strontium sulfite and barium sulfite were investigated in the atmospheres of argon and air. the thermal behaviours of magnesium sulfite were different from those of the other two sulfites. The oxidation of magnesium sulfite in air does not occur.The bonding state of the SO ₃ ^2– in each sulfite was compared. The SO ₃ ^2– in magnesium sulfite was coordinated through the sulfur, while those in the other sulfites were coordinated through the oxygen.It appears that the difference in thermal behaviour between magnesium sulfite and the other sulfites depend upon the difference in bonding state of the SO ₃ ^2– We wish to thank Mr. K. Takahashi of MAC Science Inc. for TG and DTA measurements, mass spectra in Ar and his valuable discussions.     

Synthesis and antifungal activity of novel 14-membered benzomacrolides, as galbonolide analogues

Asymmetric total synthesis of benzene analogues of galbonolide, a 14-membered antifungal macrolide, possessing a benzene ring instead of a conjugated diene structure, was achieved starting from chiral 1-aryl-1-propanol obtained by enzyme-catalyzed kinetic resolution with high enantioselectivity. Representatively, a method for the introduction of a methylthio and chloride function at the vinyl position was also established. The resulting analogues unfortunately exhibited very little antifungal potency in comparison with galbonolide A.