Conversion of α-diazoketones to 1-bromo-2-alkyl- or 2-arylpent-4-en-2-ols using Tin-mediated allylation/propargylation

High yielding and mild conditions to prepare of 1-bromo-2-alkyl- or 2-arylpent-4-en-2-ols/1-bromo-2-alkyl-or 2-arylpent-4-yn-2-ols from α-diazoketones which involves allylation/propargylation with successive bromide insertion using in-situ generated allyltin bromide/or propargyltin bromide from activated tin metal and allyl/or propargyl bromide

Stereoselective synthesis of the ABCD ring framework of azaspiracids

A stereoselective synthesis of the ABCD ring framework of azaspiracid-1 and azaspiracid-3 has been achieved using a tandem bis-spiroketalization protocol in the presence of a mild proton source from 1,4-diketone precursor. A tetrahydrofuran intermediate with the correct stereochemistry for the D ring of azaspiracids-1 and 3 was then taken through a linear sequence of reactions to afford the desired diketone precursor. The D-ring of azaspiracid-1 was then constructed by employing a Sharpless asymmetric dihydroxylation followed by etherification using a homoallyl derivative. The structure of the ABCD ring framework with four contiguous rings was established by extensive NMR analysis

Condensation of orthoacetates with aldehydes: a new strategy for the preparation of α,β-unsaturated esters

α,β-Unsaturated esters are formed in good yields when aldehydes are heated with orthoacetates in the presence of a catalytic amount of phenol

In pursuit of natural product leads: Synthesis and biological evaluation of 2-[3-hydroxy-2-[(3-hydroxypyridine-2-carbonyl)amino]phenyl]benzoxazole-4- carboxylic acid (A-33853) and its analogues: Discovery of N-(2-benzoxazol-2- ylphenyl)benzamides as novel antileishmanial chemotypes

The first synthesis and biological evaluation of antibiotic 31 (A-33853) and its analogues are reported. Initial screening for inhibition of L. donovani, T. b. rhodesiense, T. cruzi, and P. falciparum cultures followed by determination of IC50 in L. donovani and cytotoxicity on L6 cells revealed 31 to be 3-fold more active than miltefosine, a known antileishmanial drug. Compounds 14, 15, and 25 selectively inhibited L. donovani at nanomolar concentrations and showed much lower cytotoxicity. © 2008 American Chemical Society

Wacker oxidation of terminal olefins in a mixture of [bmim][BF<SUB>4</SUB>] and water

A simple and efficient PdCl<SUB>2</SUB>/CuCl catalyzed oxidation of alkenes has been successfully developed using a mixture of water and the ionic liquid [bmim][BF<SUB>4</SUB>] as solvent. Starting from various types of terminal olefins, the corresponding ketones have been prepared under mild reaction conditions and obtained in good to excellent yields after a simple extraction with diethyl ether. Furthermore, it was possible to recycle and reuse the ionic liquid and the catalytic system

Solid phase synthesis of hydroxy benzothiazepinones through cyclative release under thermolysis

Hydroxy benzothiazepinones were synthesized by a simple procedure involving epoxidation of polymer bound cinnamic acids followed by nucleophilic opening of the resulting glycidic ester by o-aminothiophenol to afford the intermediate hydroxy anilino-esters which underwent cyclization cleavage on heating in DMF to release the product completely

Structure-property relationships of fluorinated carboxylic acid bioisosteres

Fluorinated alcohols and phenols are potentially useful as bioisosteres of the carboxylic acid functional group. To enable a direct comparison of the properties of fluorinated carboxylic acid surrogates with those of other commonly used, non-fluorinated bioisosteres, we conducted a structure-property relationship (SPR) study based on matched molecular pair (MMP) analyses. A series of representative examples have been characterized by experimentally determining physicochemical properties, such as acidity (pKa), lipophilicity (logD7.4), and permeability (PAMPA). The results presented can help estimate the relative changes in physicochemical properties that may be attainable by replacing the carboxylic acid functional group with fluorine containing surrogate structures

Reaction of orthoesters with alcohols in the presence of acidic catalysts: A study

1686-1692Allylic and benzylic alcohols are converted into corresponding unsymmetrical ethers when reacted with various orthoesters in the presence of montmorillonite KSF at ambient temperature. A detailed study has been undertaken to examine the mechanism and generality of these reactions with regard to various acidic catalysts, which reveal interesting competitive reactions mainly O-acetylation, together with trace amount of dimerized product. The type of the side product and their relative quantity depends upon the nature of the catalyst employed. Furthermore, the low yields of the Claisen rearrangement product obtained from allylic alcohols under heating is rationalized due to the formation of some of these products