RESUMEN
Optically active lactones are important synthons in perfume and aroma manufacturing. Therefore, developments of efficient asymmetric syntheses are desired. Organocatalytic asymmetric alpha-hydroxymethylations of cyclopentanone with aqueous formaldehyde have been developed, to furnish the corresponding alpha-(hydroxymethyl)cyclopentanone with high enantioselectivity. Further chemical transformation of alpha-(hydroxymethyl)cyclopentanone gave the key intermediate for jasmine lactone, which is widely found in fruits and flowers.
Asunto(s)
Ciclopentanos/química , Formaldehído/química , Lactonas/química , Catálisis , Lactonas/síntesis química , Estereoisomerismo , Treonina/química , Agua/químicaRESUMEN
We have developed a direct, asymmetric Michael reaction that can be performed in brine or seawater without addition of organic solvents. A bifunctional catalyst with long hydrophobic alkyl chains efficiently catalyzed Michael reactions and afforded the desired products in excellent yield with high enantiomeric excess, even when only an equal molar ratio of the donor to acceptor was used.
RESUMEN
We have developed direct asymmetric cross-aldol reactions that can be performed in water without addition of organic solvents. A bifunctional catalyst with a long hydrophobic alkyl chain efficiently catalyzed the reactions and afforded the desired aldol products in excellent yield with high enantiomeric excess, even when only an equal molar ratio of the donor and acceptor was used. These results reveal an effective design strategy for the development of aqueous organocatalytic systems.
RESUMEN
The synthesis of (E)-3,7-dimethyl-2-octene-1,8-diol (1), which was isolated from the hairpencils of male Danaus chrysippus (African Monarch), was investigated. The key step of the sequence involves asymmetric desymmetrization of the 1,3-propanediol 7 with lipase, in which high enantioselectivity was observed. Total synthesis afforded (S)-1 in 12 steps and 26% overall yield from readily available geraniol.
Asunto(s)
Alcoholes/síntesis química , Alquenos/síntesis química , Mariposas Diurnas/química , Lipasa/química , Monoterpenos Acíclicos , Alcaligenes/enzimología , Alcoholes/química , Animales , Burkholderia cepacia/enzimología , Candida/enzimología , Catálisis , Lipasa/metabolismo , Masculino , Glicoles de Propileno/química , Pseudomonas fluorescens/enzimología , Estereoisomerismo , Terpenos/químicaRESUMEN
Lipase-catalyzed kinetic resolution of the N,N-dialkyl-3-benzyloxymethyl-4-hydroxybutanamide 10a,b afforded the acetate 11a,b with (R) configuration, whereas the N-monoalkyl-3-benzyloxymethyl-4-hydroxybutanamide 10c-e gave the acetate 11c-e with (S) configuration. The butanamide 10 smoothly cyclized to give chiral 4-benzyloxymethyldihydrofuran-2-one 9 without racemization, which was effectively transformed into highly stereocontrolled virginiae butanolide C (VB C).