Short synthetic sequences commencing with the photosensitized [2 + 2]-cycloaddition reactions of maleic anhydride with either allyl alcohol or propargyl alcohol have been elaborated to provide access to 1,2,3-trisubstituted cyclobutanes with three differentiated one-carbon substituents and complementary stereochemical patterns. These intermediates were used to prepare three discrete stereo- and...

The acid-catalyzed three-component reaction of terminal alkynes, benzylic alcohols, and simple arenes provides convenient and atom-economic access to an array of both Z- and E-isomers of trisubstituted alkenes with excellent stereoselectivity by switching reaction temperature and acidic catalysts.

An efficient palladium-catalyzed asymmetric hydrogenation of fluorinated aromatic pyrazol-5-ols has been developed via capture of the active tautomers. A wide variety of 2,5-disubstituted and 2,4,5-trisubstituted pyrazolidinones have been synthesized with up to 96% and 95% ee, respectively. The hydrogenation pathway includes Brønsted acid promoted tautomerization of pyrazol-5-ols and Pd-catalyz...

A novel strategy has been identified for the regioselective synthesis of 3,4-disubstituted quinolines and 2,3,5-trisubstituted pyrroles from simple alkenes via anti-Markovnikov selectivity under palladium catalysis. The salient features are synthesis of two different heterocycles, readily available starting materials, broad substrate scope, moderate to good yields and use of molecular oxygen as...

A method to prepare highly conjugated indenes efficiently by iron(III) chloride-catalysed dimerisation of trisubstituted propargylic alcohols under very mild conditions at room temperature is described. The reactions are rapid and operationally straightforward, giving the indene products in good yields and regioselectivity.

The reaction of acetylides with sulfonyl azides was found to selectively form 1,5-substituted sulfonyl triazoles. This reaction thus provides access to the regioisomeric product as compared to the popular copper-catalyzed azide-alkyne cycloaddition. The reaction is efficient and selective with a variety of alkyne sources and sulfonyl azides and can incorporate an additional electrophile to yiel...

Preparation of new types of trisubstituted oxazoles is realized via chemoselective O-acylations and intramolecular Wittig reactions with ester functionalities using in situ formed phosphorus ylides as key intermediates. A plausible reaction mechanism for this undiscovered chemistry is also proposed based on the existence of expected and rearranged isomeric oxazoles.

L-Histidine and imidazole (the histidine side chain) significantly increase cAMP accumulation in intact LLC-PK1 cells. This effect is completely inhibited by isobutylmethylxanthine (IBMX). Histidine and imidazole stimulate cAMP phosphodiesterase activity in soluble and membrane fractions of LLC-PK1 cells suggesting that the IBMX-sensitive effect of these agents to stimulate cAMP formation is no...

We have studied the mechanism by which lysosomotropic detergents kill baby hamster kidney cells. Lysosomotropic detergents are lysosomotropic amines (compounds with pK between 5 and 9, such as imidazole or morpholine) containing straight-chain hydrocarbon "tails" of 9-14 carbon atoms (Firestone, R. A., J. M. Pisano, and R. J. Bonney. 1979, J. Med. Chem., 22:1130-1133). Using lucifer yellow CH a...

An efficient and mild synthesis of trisubstituted furans, starting from α,β-unsaturated ketones, tributylphosphine, and acyl chlorides, is described. The strategy employs the intramolecular Wittig protocol as a key step to install the crucial furan ring, leading to a wide variety of highly functional furans in one step.