99631-16-0Relevant academic research and scientific papers
Enantioselective hydrogenation of levulinic acid esters in the presence of the RuII-BINAP-HCl catalytic system
Starodubtseva,Turova,Vinogradov,Gorshkova,Ferapontov
, p. 2374 - 2378 (2005)
The rate of hydrogenation of γ-ketoesters MeCOCH2CH 2COOR (R = Et, Pri, But) in the presence of the chiral RuII-BINAP catalyst (BINAP is 2,2′- bis(diphenylphosphino)-1,1′-binaphthyl) greatly increases upon the addition of 5-10 equivalents of HCl with respect to ruthenium. In the hydrogenation of ethyl levulinate, the optically active γ-hydroxy ester initially formed would cyclize by ～95% to give γ-valerolactone with optical purity of 98-99% ee. When the Ru(COD)(MA)2-BINAP-HCl catalytic system is used (COD is 1,5-cyclooctadiene, MA is 2-methylallyl), complete conversion of the ketoester (R = Et) in EtOH is attained in 5 h at 60°C under an H2 pressure of 60-70 atm.
Stereodivergent preparation of valuable γ- Or δ-hydroxy esters and lactones through one-pot cascade or tandem chemoenzymatic protocols
Diaz-Rodriguez, Alba,Borzeicka, Wioleta,Lavandera, Ivan,Gotor, Vicente
, p. 386 - 393 (2014/03/21)
A series of enantiopure hydroxy esters and lactones has been synthesized in a chemodivergent manner via alcohol dehydrogenase (ADH) reduction of the corresponding keto esters by means of cascade or tandem protocols. Thus, ADH from Rhodococcus ruber (ADH-A) or Lactobacillus brevis (LBADH) afforded both antipodes in a very selective way when dealing with small derivatives. With bulkier substrates, ADH from Ralstonia sp. (RasADH) was successfully employed to achieve the synthesis of enantioenriched γ- or δ-hydroxy esters. To isolate the corresponding lactones, two different approaches were followed: a cascade reaction by spontaneous cyclization of the hydroxy ester intermediate, or a one-pot two-step tandem protocol. Moreover, a chemoenzymatic route was designed to obtain a chiral brominated lactone, which enabled further modifications in a sequential fashion by Pd-catalyzed reactions, affording relevant functionalized lactones.
