The reaction of 17,17-dichloro-androst-16(E)-chloromethylene with secondary amine base afforded substitution products exocyclic D-ring ketones, in contrast to the alkaline which cleaved steroidal des-D formyl alkyne. alkyne was employed prepare annulated isoxazolo steroid via 1,3-dipolar nitrile oxide cycloaddition reaction.

2-Silyl-cyclobutene(di)ones are obtained by an addition/substitution approach on dimethyl squarate using silyl anions. The acetal and in particular the thioacetal derivatives readily undergo electrocyclic ring opening to reactive silyl(vinyl)ketenes.

Substitution of a 6-membered by a 5-membered ring upper half in the light driven second generation molecular motors resulted in a dramatic increase of the speed of rotation.

Photoswitching and fluorescent properties of sulfone derivatives of 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclopentene, 1-5, having methyl, ethyl, n-propyl, i-propyl, and i-butyl substituents at the reactive carbons (2- and 2'-positions) of the thiophene 1,1-dioxide rings were studied. Diarylethenes 1-5 underwent isomerization reactions between open-ring and closed-ring forms upo...

Rh-catalysed conjugate additions of 2-aminophenyl boronic acid derivatives were exploited in diastereoselective and asymmetric syntheses of tetrahydroquinolines. In both cases, combinatorial variation of the substitution of the tetrahydroquinoline ring system was possible.

The effect of aromatic ring substitution in the polyester polyol molecule on its physicochemicalproperties and conditions synthesis, fire resistance thermal stability polyurethanefoams was investigated. greater number terephthalic units results viscosityand reactivity during foam formation. obtained foams were characterized by higher thermalstability (TGA) (oxygen index, single flame test).

A general and efficient synthesis of carbocyclic and hexenopyranosyl nucleosides has been developed. The strategy combines three key transformations: an asymmetric aldol addition to establish the relative and absolute configuration of the pseudosugar, a ring-closing metathesis to construct the pseudosugar ring, and a Trost-type palladium(0)-mediated substitution to assemble the pseudosugar and ...

The design, synthesis and biological activities of potent pyrazole-based tricyclic CB1 receptor antagonists (2) are described. The key synthetic step involves the ring closure of the lithiated alpha, gamma-keto ester adduct (4). The optimal nitroderivative (28) in this series exhibits a high CB1 receptor affinity (pKi=7.2) as well as very potent antagonistic activity (pA2=8.8) in vitro. The reg...

A number of wogonin derivatives have been synthesized as congeners of wogonin and evaluated for their inhibitory activities of PGE2 production. Wogonin derivatives modified at the B ring of wogonin were obtained from 2,4-Dihydroxy-3,6-dimethoxyacetophenone (1) via several steps. Most wogonin derivatives exhibited much reduced inhibitory activities against COX-2 catalyzed PGE2 production compare...