title: Structural determination of molecular stereochemistry using VCD spectroscopy and a conformational code: absolute configuration and solution conformation of a chiral liquid pesticide, (R)-(+)-malathion.
abstract: The absolute configuration and solution conformation of (R)-(+)-malathion were determined by using vibrational circular dichroism spectroscopy and a fragment-conformational search with a recently published conformational code. The determination of molecular stereochemistry was carried out without a conformational search using molecular mechanics calculations. Density functional theory calculations of the fragments of (R)-malathion, ethyl propionate, (R)-ethyl 2-(methylthio)propanoate, (R)-diethyl 2-(methylthio)succinate, and O,O,S-trimethyl phosphorodithioate were carried out, and the principal conformational features of the fragments were profiled. This fragment-conformational search reduces the time needed for the selection of the predominant conformations for (R)-malathion and significantly improves the accuracy of the determination of absolute configuration.
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba West, Tsukuba, Ibaraki, Japan. izumi.h@aist.go.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Izumi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ogata
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Nafie
authors.forename: Rina K
authors.initials: RK
authors.lastname: Dukor
mesh_terms: D002942:Circular Dichroism; D008294:Malathion / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010575:Pesticides / Q000737:chemistry*; D019999:Pharmaceutical Solutions; D013055:Spectrophotometry, Infrared; D013237:Stereoisomerism; D013816:Thermodynamics; D014732:Vibration
chemical_list: D010575:Pesticides; D019999:Pharmaceutical Solutions; D008294:Malathion