A convenient, stereospecific synthesis of (-)-phytuberin from (-)-2-carone

Tf2O- and Cu(OTf)2-Assisted Acylamination Reaction of Unactivated Alcohols with Nitriles: A One-Pot P(IV) Activation, Stereoretention in Cycloalkanols and Deprotection Approach

Described herein is a simple, novel, one-pot acylamination reaction of unactivated alcohols. This reaction employs the combination of PCl₃ and triflic anhydride (Tf₂O) or copper triflate Cu(OTf)₂, which serves as a source of P(IV)-activated complex for nitriles to react under the Ritter-type mechanism. The synthetic utility of Tf₂O-promoted reactions was demonstrated by its effectiveness to generate different acylaminated products. By employing Cu(OTf)₂, this method represents a rare example of α-selective acylamination reaction. With chiral cycloalkanols, using the Cu(OTf)₂-promoted procedure, acylaminated products are formed with complete retention of configuration. The synthetic utility of the copper-assisted reaction in acetonitrile was readily demonstrated as a mild deprotection strategy.

A convenient approach to an advanced intermediate toward the naturally occurring, bioactive 6-substituted 5-hydroxy-4-aryl-1H-quinolin-2-ones

An advanced intermediate for the total synthesis of the 5-hydroxy-4-aryl-3,4-dihydro-1H-quinolin-2-one natural products and a 3,4-bisdesoxy analog of peniprequinolone were synthesized.

The 3,4-dioxygenated 5-hydroxy-4-aryl-quinolin-2(1H)-one alkaloids. Results of 20 years of research, uncovering a new family of natural products

The title alkaloids are discussed. Emphasis is placed on their isolation, source microorganisms and structure, as well as relevant biological activities and synthetic progress.

The total synthesis of Cannabisin G

A convenient method for the synthesis of lignanamide Cannabisin G, starting from the vanillin, was developed. The convergent synthesis was based on the Stobbe reaction as C-C bond-forming steps to give the skeleton of lignan, which was condensed with a derivative of tyramine to obtain synthetic Cannabisin G for the first time.

Synthesis of phytuberin. 4-endo-tet acid-catalyzed cyclization of alpha-hydroxy epoxides

The total synthesis of phytuberin, a phytoalexin of the Solanum genus, from (-)-alpha-santonin is reported. The key steps include (a) reductive cleavage of the C-O bond of the gamma-lactone with concomitant protection of the C1 double bond, (b) Sharpless stereocontrolled hydroxy-assisted epoxidation of allylic alcohol 6 and simultaneous deprotection of the C1 double bond, (c) a rare 4-endo-tet acid-catalyzed cyclization of an alpha-hydroxy epoxide, and (d) an unprecedented 4-exo selenocyclization of a homoallylic alcohol.

Hydrogenation of 1-Hexene and Hexadienes by Ultrafine Pd Particles Supported on the Surface of PrPO(4) Hollow Particles

Novel fine polymer particles containing ultrafine Pd particles dispersed on the surface of core shell [core, poly(styrene-co-acrylic acid); shell, PrPO(4)]-type microspheres were prepared by the emulsifier-free emulsion polymerization of styrene with acrylic acid followed by the addition of PdCl(2) and a mixture of Pr(NO(3))(3) and NaH(2)PO(2). Pyrolysis of the resulting polymer particles at 900 degrees C provides organic polymer-free hollow particles (diameter, 473-586 nm) composed of Pd metal and PrPO(4). Hydrogenation of 1-hexene, trans-1,3-hexadiene, trans-1,4-hexadiene, and 1,5-hexadiene using the resulting Pd/PrPO(4) particles (reactant/Pd = 500 mol/mol) as catalyst revealed very high activity, especially for hydrogenations of 1-hexene and 1,5-hexadiene as compared with conventional Pd particles/Al(2)O(3) and Pd particles on powdered PrPO(4). Copyright 1999 Academic Press.

Allylindation of 6-Substituted 2-Hydroxy-1-tetralones in Aqueous and Organic Media. Stereochemistry and Competition Studies

A systematic investigation of the stereoselectivity associated with coupling reactions involving the allylindium reagent and 6-substituted 2-hydroxy-1-tetralones is presented. In each instance, the allylations were carried out in water, 50% aqueous THF, and dry THF. The extent of 1,2-induction was found to be highest in THF-H(2)O (1:1) and to favor the trans diol isomer. Somewhat lower levels of stereochemical bias in the same direction were observed in pure water. However, further erosion of this trend was noted for those reactions performed in THF, such that a modest crossover in product distribution became apparent in certain examples. On the basis of competition experiments, both reaction trajectories give evidence of proceeding via chelated intermediates. The extent of stereoinduction was found to be in line with the normal predilection of 2-cyclohexenones for axial attack, which is the process believed to be beset with minimal torsional effects. The substituents situated para to the ketone carbonyl do not exert a very large influence on product distribution, although electronic effects are evident in the context of the competition studies. A mechanistic model which integrates these findings is offered.

CHEMOSELECTIVE CATALYTIC HYDROGENATION OF ALKENES BY LINDLAR CATALYST

Commercially available Lindlar catalyst (10% by weight) in methanol, selectively hydrogenates various alkenes in the presence of benzyl ether and benzyl amine functionalities.

Carbocyclic oxetanocins lacking the C-3' methylene

Using the observation that the side effects of aristeromycin (carbocyclic adenosine) were reduced by removing the methylene at the center in aristeromycin where phosphorylation occurs, derivatives of carbocyclic oxetanocin A (4a), oxetanocin G (4b), and 2-aminooxetanocin A (16) lacking the 3'-methylene have been prepared in racemic form. The only viruses for which an appreciable inhibitory effect of the compounds (minimum inhibitory concentration ranging from 1 to 40 microg/mL) was noted were herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV). However, when directly compared for their antiviral potency against HSV-1 with their parents oxetanocin A and oxetanocin G, compounds 4a and 4b proved clearly less active.