32174-38-2Relevant articles and documents
Chemoenzymatic Preparation of Enantiomerically Enriched (R)-(–)-Mandelic Acid Derivatives: Application in the Synthesis of the Active Agent Pemoline
Potera?a, Marcin,Dranka, Maciej,Borowiecki, Pawe?
, p. 2290 - 2304 (2017/05/01)
The enantioselective resolution of several racemic derivatives of mandelic acid methyl ester catalyzed by lipases from Pseudomonas fluorescens (Amano AK) or Burkholderia cepacia (Amano PS-C II and Amano PS-IM) has been achieved. A gram-scale lipase-mediated kinetic resolution approach has been developed that allows the facile synthesis of the corresponding methyl (R)-(–)-mandelates with excellent enantiomeric excesses (up to >99 % ee) and reaction enantioselectivity (E values up to >200). The dopaminergic agent pemoline, used in the treatment of attention-deficit hyperactivity disorder (ADHD) and narcolepsy, was synthesized with 98 % ee in a straightforward route by condensing the prepared methyl (R)-(–)-mandelate with guanidine hydrochloride under basic conditions. The desired (R)-(+)-pemoline in optically pure form (>99 % ee) was obtained after two recrystallizations from ethanol. However, it was confirmed by chiral HPLC that optically active pemoline undergoes racemization in methanol solution.
Chiral cobalt-catalyzed enantioselective aerobic oxidation of α-hydroxy esters
Alamsetti, Santosh Kumar,Sekar, Govindasamy
supporting information; experimental part, p. 7235 - 7237 (2010/12/24)
A chiral cobalt-catalyzed enantioselective aerobic oxidative kinetic resolution of (±)-α-hydroxy esters, using molecular oxygen as a sole oxidant, is reported and a maximum of selectivity factor (s) 31.9 was achieved with >99% enantiomeric excess for unreacted α-hydroxy esters.
Enantioselective homoallyl-cyclopropanation of dibenzylideneacetone by modified allylindium halide reagents-rapid access to enantioenriched 1-styryl-norcarene
Lloyd-Jones, Guy C.,Wall, Philip D.,Slaughter, Jennifer L.,Parker, Alexandra J.,Laffan, David P.
, p. 11402 - 11412 (2007/10/03)
Dibenzylideneacetone (8) reacts with in situ-generated allylindium halide reagents to yield the product of a homoallyl-cyclopropanation reaction: 2-(3″-butenyl)-1,1-bis[(E)-2′-phenylethenyl]cyclopropane (9), which proceeds via step-wise cleavage of the C{double bond, long}O bond and delivery of two allyl fragments from the reagent. A range of enantiomerically enriched ligands have been tested as stoichiometric asymmetric modifiers for this process. Enantiopure compounds such as cinchona alkaloids, ephedra, aminoalcohols and tartaric acid derivatives, which have proven of utility as asymmetric modifiers for the indium-mediated allylation of aldehydes and ketones, were very inefficient in the process 8→9. However, mandelic acid derivatives, in particular mandelates, were found to be of significant potential. The absolute stereochemistry of the cyclopropane 9 has been determined by degradation to 1,1-dicarboxymethyl-2-butylcyclopropane, converging with an independent enantioselective synthesis starting from hexene. Under optimised conditions, viz. using allylindium iodide reagents and working-up with aqueous Na2SO3 to avoid iodine-mediated polymerisation, (S)-9 can be generated in 86% yield and with (S)-methyl mandelate as modifier useful enantiopurity (94/6 er) was observed. The cyclopropane product ((S)-9) undergoes RCM using standard conditions to afford a norcarene unit ((1S,6S)-1-(E)-2′-(phenylethenyl)-bicyclo[4.1.0]hept-2-ene) without loss of enantiopurity.
