Stereoselective Synthesis of δ-Lactones from 5-Oxoalkanals via One-Pot Sequential Acetalization, Tishchenko Reaction, and Lactonization by Cooperative Catalysis of Samarium Ion and Mercaptan
作者:Jue-Liang Hsu、Jim-Min Fang
DOI:10.1021/jo016058t
日期:2001.12.1
sequence of acetalization, Tishchenko reaction and lactonization. The deliberative use of mercaptan, by comparison with alcohol, is advantageous to facilitate the catalytic cycle. The reaction mechanism and stereochemistry are proposed and supported by some experimental evidence. Such samarium ion/mercaptan cocatalyzed reactions show the feature of remote control, which is applicable to the asymmetric synthesis
Efficient and flexible synthesis of chiral γ- and δ-lactones
作者:Andreas Habel、Wilhelm Boland
DOI:10.1039/b801514g
日期:——
An efficient and highly flexible synthesis for chiral γ- and δ-lactones with high enantiomeric purity is described (>99% ee and 57â87% overall yield). The protocol involves alkylation of chiral 1,2-oxiranes with terminally unsaturated Grignard reagents. Subsequent oxidative degradation (OsO4âOxone) of the terminal double bond from chiral alk-1-en-5-ols and alk-1-en-6-ols affords 4- or 5-hydroxy acids and γ- and δ-lactones after acidic workup. The flexibility and efficiency of the protocol is illustrated by the synthesis of several alkanolides and alkenolides, hydroxy fatty acids and dihydroisocoumarins.
Both enantiomers of a series of delta-lactones (e.g., delta-decalactone, delta-dodelactone, and delta-hexadecalactone) were synthesized stereoselectively by Novozym 435-catalyzed resolution. Furthermore, only (S)-enantiomers of delta-lactones were synthesized with a combination of Novozym 435-catalyzed resolution and Mitsunobu reaction.
Cooperative Catalysis of Samarium Diiodide and Mercaptan in a Stereoselective One-Pot Transformation of 5-Oxopentanals into δ-Lactones
作者:Jue-Liang Hsu、Chao-Tsen Chen、Jim-Min Fang
DOI:10.1021/ol9911526
日期:1999.12.1
[GRAPHICS]We demonstrate a general method for conversion of various 5-oxopentanals to substituted delta-lactones and 1-oxa-2-decalones by the synergistic catalysis of samarium diiodide and 2-propanethiol (or disulfide), The deliberate use of mercaptan is advantageous to facilitate the catalytic cycle, This method shows high stereoselectivities, and an enantioselective procedure is feasible by using the chiral mercaptan (1R,2S)-1 phenyl-2-(N-acetamido)propanethiol as a promoter.
Enzyme assisted synthesis of enantiomerically pure δ-lactones
作者:Bernhard Haase、Manfred P. Schneider
DOI:10.1016/s0957-4166(00)80146-9
日期:1993.5
Both enantiomeric series of a wide variety of optically pure 6-alkylated delta-lactones - saturated as well as unsaturated - were prepared via an enzyme mediated route. The key reaction step is the nucleophilic ring opening of enantiomerically pure alkyl-oxiranes, accessible via the corresponding beta-hydroxythioethers which can be obtained enantiomerically pure via enzyme catalyzed kinetic resolutions.