SummaryThe enantiomers of phenoxypropionic acid type herbicides have been resolved by capillary gas chromatography employing modified cyclodextrins as chiral stationary phases. Excellent separations were obtained with columns containing a 1 :I mixture of per-0-pentylated and per-0-methylated 6-cyclodextrin.pesticides and herbicides may differ by orders of magnitude, but little is known about their selective action. It has been found that the activity of the D( +) forms of some chiralphenoxypropionic acid derivatives (1-3; Figure 1) which are used as herbicides is about twice as high as that of the racemates.The enantiomers of the methyl esters of mecoprop and dichlorprop were also resolved on octakis(3-O-butyryl-2,6-di-O-penty1)y-cyclodextrin. On this phase the order of elution of the enantiomers was temperature-dependent, the elution order being reversed as the temperature passed through the isoenantioselective temperature. This is the first time such behavior has been observed with cyclodextrin derivatives.The enantiomers of the polychlorinated polycyclic pesticides cis-and trans-chlordane, oxychlordane, heptachlor, heptachlorepoxide, and three chiral organophosphorus pesticides could be resolved using selectively derivatiied cyclodextrin derivatives.

SummaryTransferring the site of specific substitution of dipentylated cyclodextrins with methyl or acyl residues from the secondary 3-hydroxyl group to the primary 6-hydroxyl group was expected to provide new information on the mechanism of chiral recognition-The 3-position points towards and the 6-position points away from the cyclodextrin cavity which via inclusion complex formation is supposed to play a major role in chiral separation.The "inverse" 6-0-acyl-2,3-di-0-pentyl-cyclodextrins displayed almost no enantioselectivity but the corresponding 6-0-methyl derivatives are a versatile supplement to the chiral capillary GC phases nowadays available. Among the compounds that could be enantiomerically resolved are alcohols, amino acids, alkyl halides, bicyclic ethers, acetals, olefins, other hydrocarbons and chiral pharmaceuticals.

SummarySelectively alkylated cyclodextrins have been used to resolve the enantiomers of 2,2' alkylated biphenyls.The configurational stability of 2,2'-dimethyl and 2,2'-diethyl biphenyls is insufficient for gas chromatographic separation even at ambient temperature. 2-lsopropyl-2'-t-butyl-and 2,2'-di-t-butylbiphenyl are configurationally stable under the conditions applied, whereas 2,2'-diisopropyl-and 2,2'-bis(trifluoromethyl)biphenyl show temperature-dependent interconversion of the enantiomers during chromatography. The gas chromatographic separation of the enantiomers of some ortho trichlorinated biphenyls carrying 4, 5, and 6 chlorine substituents has been demonstrated for the first time.

Iron complexes with 1,Cdiaza-I ,3-diene (DAD) ligands catalyze the cyclodimerization of simples dienes."' A 1 : 1 mixture of frun.v-I .3-pentadiene and isoprene, for example, can be dimerized by 1 a activated with organomagnesium com-pounds121 providing racemic 1,7-dimethyl-I ,5-cyclooctadiene 2 in 88 YO yield (Scheme 1). We have found that reactions with precatalyst 1 b obtained from the C, symmetric (1R)menthyl-DADL3I deliver optically active (-)-I ,7-dimethyl-1,5-cyclooctadiene (-)-2 in 89 % yield with up to 61 % ee. & 0.7%"(CJ6)Mg" + 0.5% l b -ll°C/ 14 d -2 89% (6l%@ Scheme 1. Enantioselective codimeriaation of isoprene and truns-1.3-pentadiene. Dimethylcyclooctadiene (DMCOD) 2 isomerizes readily under acidic conditions to derivatives of bicyclo[3.3.0]octane (Scheme 2). The cationic intermediate may be captured stereoselectively by a nucleophile resulting in the endo product (3-5). Alternatively, elimination or rearrangement/ elimination may provide olefins like 7-9. This elimination is 3a,R= Ac 3c, R=Me OR 3d, R= I 3 Jb, R= CHO Ac

Halothane (I), enflurane (II), and isoflurane (III), which are among the most important inhalation anesthetics, are currently administered as racemic mixtures. The pure enantiomers have not been described, and no analytical method for resolving the commercially available racemic mixtures has been reported. Complete optical resolution of (+/-)-I and (+/-)-III on per-n-pentylated alpha-cyclodextrin (Lipodex A) and of (+/-)-II and (+/-)-III on octakis(6-O-methyl-2,3-di-O-pentyl)-gamma-cyclodextrin capillary columns has been achieved, making rapid and convenient determination of enantiomeric ratios in samples of all three of these anesthetics possible.