Fenvalerate four chiral isomers

In addition, three types of lipophilic conjugates have been found in pyrethroid metabolism studies (Fig. 4). They are cholesterol ester (fenvalerate) [15], glyceride (3-PBacid, a common metabolite of several pyrethroids) [16], and bile acid conjugates (fluvalinate) [17]. It is noteworthy that one isomer out of the four chiral isomers of fenvalerate yields a cholesterol ester conjugate from its acid moiety [15]. This chiral-specific formation of the cholesterol ester has been demonstrated to be mediated by transesterification reactions of carboxylesterase(s) in microsomes, not by any of the three known biosynthetic pathways of endogenous cholesterol esters... 

Takamatsu, Y. Kaneko, H. Abiko, J. Yoshitake, A. Miyamoto, J. In vivo and in vitro stereoselective hydrolysis of four chiral isomers of fenvalerate. J. Pesticide Sd. 1987, 12, 397 4. 

Esfenvalerate consists primarily of isomer D. Tan et al. (2007) reported on the complete separation of the four fenvalerate isomers by using a novel CSP prepared by connecting (R)-l-phenyl-2-(4-methylphenyl)ethylamine (PTE) amide derivative of (S)-isoleucine to aminopropyl silica gel, through a 2-amino-3,5-dinitro-l-carboxamido-benzene unit. The mobile phase was hexane 1, 2-dichloroethane 2-propanol (97.45 2.50 0.05). The order of elution was C, B, A, and D, respectively. In an earlier study, Papadopoulou-Mourkidou (1985) used a chiral column (BAKERBOND) and a mobile phase of 0.1% methanol, 0.3% 2-propanol, and 99.6% hexane (by volume) to separate all four isomers of fenvalerate. 

Fenpropathrin Fenpropathrin has two isomers (2 = 2) by virtue of possessing one chiral center. Tan et al. (2007) reported the separation of the two isomers of fenpropathrin with a CSP column (that is described in the above paragraph as having also separated the four isomers of fenvalerate) (Table C8, Appendix C). The mobile phase was -hexane 1, 2-dichloroethane 2-propanol (96.8 3.0 0.2). The A isomer chromatographed prior to the B isomer. 

Table D7, Appendix D, gives the chemical structure of parent pyrethroid and metabolites of fenvalerate (Kaneko and Miyamoto 2001 Kaneko 2010). Fenvalerate or Pydrin (CAS no. 51630-58-1) contain equal amounts of the four chiral isomers (Appendix B, Table B14), while esfenvalerate (CAS no. 66230-04-4), shown in Table B14, is comprised of 84% of the D isomer.

Fenvalerate[(RS)-a-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)iaovalerate] consists of four optical isomers due to the presence of two chiral carbons in the acid and alcohol moieties. Of the four isomers, one specific isomer ([2R,CXS]) was preferentially metabolized in mammals including rats and mice to a cholesterol ester which was formed by condensation of the acid moity with cholesterol. This conjugate does not seem to be produced via three known endogenous biosynthesis routes of cholesterol esters, but via transesterification mediated by microsomal... 

Fenvalerate Fenvalerate has four isomers (2 = 4). A CHIRALCEL OD colunm separated the enantiomer pair I (isomers A + D) from II (isomers B + C) (Li et al. 2006) (Table C7, Appendix C). Of the four individual isomers, the first and secrnid peaks were only partially resolved (Li et al. 2009). Huang et al. (1991) resolved fenvalerate into four well-separated peaks on a Pirkle-type 1-A chiral HPLC colunm using 99.9 0.1 hexane/isopropanol (v/v) as the mobile phase. The respective elution order was B, C, D, and A. The enantiomer pair II eluted before pair I. 

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