Separation and identification of indene–C70 bisadduct isomers

Following an initial work on the isolation of a single geometric isomer from an indene–C70 bisadduct (IC70BA) mixture, we report the full fractionation and identification of the bisadduct species in the material. Eleven fractions of IC70BA isomers were separated by high-performance liquid chromatography. A number of fractions contained relatively pure isomer species and their configuration were deduced using a variety of analytical techniques including 1H and 13C NMR and UV–vis spectroscopy. The electrochemical properties and the organic solar cell device performance were investigated for fractions where a reasonable quantity of sample could be isolated.

Group-assisted purification (GAP) chemistry for the synthesis of Velcade via asymmetric borylation of N-phosphinylimines

A new approach to the anticancer drug Velcade was developed by performing asymmetric borylation of an imine anchored with a chiral N-phosphinyl auxiliary. Throughout the 7-step synthesis, especially in the imine’s synthesis and in the asymmetric borylation reactions, operations and work-up were conducted in simple and easy ways without any column chromatographic purification, which defines the GAP (group-assisted purification) chemistry concept. It was found that the optically pure isomer (dr > 99:1) can be readily obtained by washing the crude mixture of the asymmetric borylation reaction with hexane; the chiral N-phosphinyl auxiliary can be easily recovered after deprotection is finished. Several other N-phosphinylimines were also investigated for the asymmetric borylation reaction. The absolute configuration of the borylation product was confirmed by single crystal X-ray diffraction analysis.

Micelle Enhanced Fluorimetric and Thin Layer Chromatography Densitometric Methods for the Determination of (±) Citalopram and its S - Enantiomer Escitalopram

Two sensitive and validated methods were developed for determination of a racemic mixture citalopram and its enantiomer s-(+)escitalopram. The first method was based on direct measurement of the intrinsic fluorescence of escitalopram using sodium dodecyl sulfate as micelle enhancer. This was further applied to determine escitalopram in spiked human plasma, as well as in the presence of common and co-administerated drugs. The second method was TLC densitometric based on various chiral selectors was investigated. The optimum TLC conditions were found to be sensitive and selective for identification and quantitative determination of enantiomeric purity of escitalopram in drug substance and drug products. The method can be useful to investigate adulteration of pure isomer with the cheap racemic form.

Preparation of aromatic polyamides from newly separated optically pure phenylindanedicarboxylic acid and their application to enantioseparation

An optically pure isomer of 1,l,3.-trimethyl-3-phenylindane-4',5-dicarboxylic acid (PIDA) was obtained by introduction of racemric PIDA to a diester of the optically pure alcohol. D-(-)-pantolactone, followed by hydrolysis of the separated stereoisomer of the diester. Optically active aromatic polyamides (aramids) were synthesized by the reaction of the optically pure PIDA with various aromatic diamines. The specific rotations of these aramids ranged from + 284 to +4416. The aramids were soluble in organic solvents such as N,N-dimethylacetamide, pyridine and m-cresol. These materials had glass transition temperatures over 290 'C, and did not decompose below 380 C. The solubility and thermal behaviour were almost the same as those of the racemic aramids. The optically active aramids were examined as a stationary phase for chromatographic enantioseparation. When the aramid derived from p-phenylenediamine was used for this purpose, the stereoisomers of l-phenylethylamine could be easily separated.

Approaches towards the synthesis of a 2,9,16,23-tetrasubstituted phthalocyanine as a pure isomer

Treatment of 4-neopentoxyphthalonitrile with hydrogen sulfide gas yielded 1-imino-6-neopentoxy-3-thioisoindoline and 1-imino-5-neopentoxy-3-thioisoindoline, which on alkylation with iodomethane gave 1-imino-3-methylthio-6-neopentoxyiso-indolenine and 1-imino-3-methylthio-5-neopentoxyisoindolenine. The methylthioisoindolenines readily condensed at room temperature to a mixture of tetrasubstituted phthalocyanines and a series of linear open-chained purple compounds characteristic of isoindigos, while condensation at −20 °C in the presence of zinc acetate gave, in at least one experiment, 2,9,16,23-tetraneo-pentoxyphthalocyanine as a pure isomer. The low temperature formation of phthalocyanines is remarkable and the syntheses described herein provide guidelines for the synthesis of pure isomers of 2,9,16,23-tetrasubstituted phthalocyanines. The purple and red compounds are shown to have isoindigo structures rather than a ring-opened phthalocyanine structure as previously reported.

Synthesis of isomeric and enantiomeric O-phosphonylmethyl derivatives of 9-(2,3-dihydroxypropyl)adenine

Reaction of 9-(S)-(2,3-dihydroxypropyl)adenine (I) with chloromethanephosphonyl chloride (VII) in pyridine or triethyl phosphate, or with chloromethyl(pyridinio)phosphonate (IX) in pyridine, afforded a mixture of 2'-(IV) and 3'-O-chloromethanephosphonate (V) which were separated on anion exchange resin or alkylsilica gel. Treatment of compounds IV and V with aqueous alkaline hydroxide, followed by deionization, gave 9-(S)-(2-hydroxy-3-phosphonylmethoxypropyl)adenine (VI) and 9-(S)-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (III) (HPMPA), respectively. The (R)- and (RS)-forms of III and VI were prepared analogously from the respective (R)-enantiomer and racemate of I. 9-(S)-(2,3-Dihydroxypropyl)-N6-benzoyladenine (XIV) was converted into 3'-O-(dimethoxytrityl) derivative XVII and further into 2',N6-dibenzoyl derivative XIX. Reaction of compound XVII with IX, followed by acid hydrolysis and alkaline cyclization, afforded pure isomer VI whereas pure III was prepared from XIX by reaction with VII in triethyl phosphate and subsequent alkaline cyclization.

Optisch aktive Übergangsmetall-Komplexe, LXX [1]. Darstellung der optisch aktiven Diastereomeren C5H5Fe(CO)- (CH2OCH3)P(C6H5)2N(CH3)R* mit chiralen Fe-Atomen / Optically Active Transition Metal Complexes, LXX [1]. Preparation of the Optically Active Diastereoisomers C5H5Fe(O)- (CH2OCH3)P(C6H5)2N(CH3)R* with Chiral Fe Atoms

The two diastereoisomers C5H5Fe(CO)(CH2OCH3)P(C6H5)2N(CH3)R* (Ba, b), with R* = (S)·CH(CH3)(C6H5), differing only in the Fe configuration, have been obtained by photochemical reaction of C5H5Fe(CO)2CH2OCH3 with (S)-(+)-P(C6H5)2N(CH3)R*. The optically pure isomer 3 a can be isolated by chromatography at low temperature; its chiroptical properties are discussed.

Condensation of cis-9-methyl-2-decalone with cyclic β-amino esters: synthesis and X-ray crystallography of perhydroazacyclopentaanthracenes and perhydroazabenzanthracenes

Condensation of cis-9-methyl-2-decalone, 9, with ethyl 2-pyrrolidineacetate, 10, afforded a mixture of two isomeric vinylogous amides, 11. Oxidation of either one pure isomer, 11a, or the mixture 11 to the same pyridone, 12, revealed that the two condensation products were stereoisomeric at a single carbon atom and not structural isomers. Reduction of 11a afforded the amino ketone 13. The structures assigned to 11, 12, and 13 are based on X-ray crystallographic analysis of 13.Similarly, condensation of 9 with ethyl 2-piperidineacetate, 14, afforded the isomers 15a and 15b both of which were oxidized to the same pyridone, 16. Reduction of 15a afforded 17. The structures assigned to 15, 16, and 17 are based on X-ray crystallographic analysis of 17.