Chachanat Thebtaranonth

Antimalarial sesquiterpenes from tubers of Cyperus rotundus: structure of 10,12-peroxycalamenene, a sesquiterpene endoperoxide.

Activity-guided investigation of Cyperus rotundus tubers led to the isolation of patchoulenone, caryophyllene alpha-oxide, 10,12-peroxycalamenene and 4,7-dimethyl-1-tetralone. The antimalarial activities of these compounds are in the range of EC50 10(-4)-10(-6) M, with the novel endoperoxide sesquiterpene, 10,12-peroxycalamenene, exhibiting the strongest effect at EC50 2.33 x 10(-6) M.

Developments in cyclisation reactions

Cyclisations cationiques, radicalaires et anioniques. Cyclisations catalysees par des metaux

Structures of β-senepoxide, tingtanoxide, and their diene precursors. Constituents of Uvaria ferruginea

β-Senepoxide 9, Tingtanoxide 10, and their diene precursors 7 and 8 were isolated from Uvaria ferruginea (Annonaceae). Their structures and absolute configurations were deduced using spectroscopy and chemical correlations with compounds of known stereostructures.

2,3-Dicarbomethoxy-1,3-butadiene and its reactions

Abstract The preparation of 2,3-dicarbomethoxy-1,3-butadiene from flash vacuum pyrolysis of 3 (itself obtained from methylenation of 2 ) is described. The dienes reactions with nucleophiles and dienophiles are also reported.

Pyrrolidine and α-methylene-α-lactam from the cyclization of α-(alkylaminoethyl)acrylate: Synthesis of aza-sarkomycins

Abstract Diene 1 readily adds primary amines to give 2 which can cyclize either in a Michael addition fashion or via a displacement reaction to give, respectively, pyrrolidine 3 or methylene lactam 4 which further isomerizes to 5 under the employed reaction conditions. Compound 4 can be obtained as the sole product from the reaction of diene precursor 7 with amines followed by vacuum pyrolysis.

Enantioselective synthesis of spiro[4.4]non- and spiro[4.5]dec-2-ene-1,6-diones

Abstract Spiro[4.4]non- and spiro[4.5]dec-2-ene-1,6-diones [2; n = 0 and 1] were prepared in moderate to high enantiomeric purities via asymmetric allylation of enamines 6 and ketal derivatives 7 and 8 formed from keto-esters 5, followed by a carbanionic cyclization process.

Phenylcoumarins from Ochrocarpus Siamensis

Abstract Two new phenylcoumarins, 6-butyryl-5-hydroxy-4-phenylseselin and 6-butyryl-5,7-dihydroxy-8-(3,3dimethylallyl)-4-phenyleoumarin, were isolated from the flowers of Ochrocarpus siamensis.

Meerwein–Ponndorf–Verley reaction of α-ketoepoxides. A stereocontrolled one-step synthesis of epoxy-1,3-diol monoesters

Lithium enolate 3, derived from ketoepoxide 1, adds to two molecules of an aldehyde with concomitant hydride transfer to produce 5 stereospecifically.

Synthesis of deepoxy-4,5-didehydromethylenomycin a and methylenomycin a methyl esters

[±]-Deepoxy-4,5-didehydromethylenomycin A methyl ester 8 and [±]-methylenomycin A methyl ester 9 are synthesized from anthracene adduct 2 via a common intermediate 13. Flash vacuum pyrolysis of adduct 13 gives 8, while stereospecific epoxidation of 13 followed by pyrolysis yields 9.

Stereospecific triple Michael addition

Abstract The consecutive Michael addition of a nucleophile to an α -methylene cyclopentenone, thence to methyl acrylate, occurs readily and stereospecifically, yielding bicyclo-[2,2,1]-heptanone. The reaction represents the first example of a three-component triple conjugate addition process.