Synthesis of Some New Triphenylphosphanylidenes,Alkylphosphonates, and Heterocycles of Pyrazole Derivatives and Their Antimicrobial Activity

Abstract

The reaction of 5(4H)-pyrazolone with phosphorus ylides afforded new triphenylphosphanylidene alkanone derivatives. Moreover, its benzylidene derivative reacted with Wittig–Horner reagents to give the corresponding dialkoxyphosphoryl, alkyl phosphonate, and heterocyclic products. Treatment of pyrazole-4-carbaldehyde with Wittig–Horner reagents and trialkyl phosphites gave the respective alkyl phosphonate adducts. Mechanisms accounting for the formation of the new products are discussed. The biological activity of some of the newly synthesized compounds was also examined.     

Specific Occurence of Selenium in Certain Enzymes and Amino Acid Transfer Ribonucleic Acids

Abstract

Some enzymes known to contain selenium are enumerated. In four of them which catalyze coupled oxidation-reduction reactions the selenium occurs exclusively in the form of selenocysteine residues. Their structure and function are described in detail. Two other bacterial enzymes which contain selenium in the form of a labile, readily dissociable component are also described.

Results on the isolation, identification and structure determination of selenium-containing amino acid transfer ribonucleic acids are presented. These seleno-t RNA's are shown to contain either 5-methyl-aminomethyl-2-selenouridine or other 2-selenouridine derivatives. The role of selenium in a glutamate iso-accepter species is discussed.     

A SYNTHETIC ROUTE TO 3-METHYLTHIO-2-ALKANONES STARTING FROM 3-ALKYL-2,4-PENTANEDIONES

Abstract

An efficient preparation of a 3-methylthio-2-alkanone (1) has been realized by the reaction of a 3-alkyl-2,4-pentanedione (8) with one mol-equiv of S-methyl methanethiosulfonate (4) in the presence of excess EtONa in EtOH. Furthermore, treatment of 8 with 4 and K₂CO₃ in refluxing acetone, followed by addition of MeOH and heating the resulting mixture, gave 1 in a high yield. These methods were applied to synthesis of pseudoionone.     

EFFICIENT CONVERSION OF TETRAHYDROPYRANYL (THP) ETHERS TO THEIR CORRESPONDING CYANIDES WITH TRIPHENYLPHOSPHINE/2,3-DICHLORO- 5,6-DICYANOBENZOQUINONE/n-Bu4 NCN

Tetrahydropyranyl ethers were converted to their corresponding alkyl cyanides efficiently by using the triphenylphosphine/ 2,3-dichloro-5,6-dicyanobenoquinone/n-Bu ₄ NCN system in refluxing acetonitrile with good-to-excellent yields.     

A Novel and Simple Synthesis of 2-(Trifluoromethyl)-4H-thiochromen-4-ones

Abstract

Alkyl 2-mercaptophenyl ketones react with trifluoroacetic anhydride in the presence of triethylamine to give 2-(trifluoromethyl)-4H-thiochromen-4-ones, which are transformed into the corresponding pyrazoles by treatment with hydrazine hydrate and into 1,1-dioxides by oxidation with H₂O₂ in AcOH.     

Regioselective Alkylation of Thiazolylsulfonamides: Direct and Efficient Synthesis of 3‐Alkylthiazolidene Derivatives

Various N‐3‐alkylated thiazolidenesulfonamide derivatives were efficiently prepared by the direct endo‐selective alkylation of thiazolylsulfonamides. The effects of different bases and solvents were investigated, and the NaH–THF combination was found to be the most effective at conferring high yields and endo‐selectivity.     

Chemoselective Removal of Acyloxy in 1-(Benzotriazole-1-yl)alkyl Esters and Its Application in the Preparation of β-(Benzotriazole-1-yl)alcohols

Mediated by samarium diiodide, 1-(benzotriazole-1-yl)alkyl esters 1 underwent cross-coupling with aldehydes or ketones to afford β-(benzotriazole-1-yl)alcohols 2 exclusively with the selective removal of acyloxy over benzotriazolyl.     

New Method for the Synthesis of Benzyl Alkyl Ethers Mediated by FeSO4

The synthesis of benzyl alkyl ethers from benzyl bromides and alcohols using FeSO₄ as a recoverable and reusable mediator has been described without use of base and cosolvent under mild conditions.     

Total synthesis of (+)-valienamine and (−)-1-epi-valienamine via a highly diastereoselective allylic amination of cyclic polybenzyl ether using chlorosulfonyl isocyanate

The total synthesis of (+)-valienamine and (−)-1-epi-valienamine was concisely accomplished from readily available d-glucose via a highly diastereoselective amination of chiral benzylic ether using chlorosulfonyl isocyanate, intramolecular olefin metathesis, and diastereoselective reduction of cyclic enone using l-Selectride as the key steps.