Chiroptical detection during liquid chromatography 7. The rotation angle/absorbance ratio of chiral molecules. Its possible use for on-line analysis during preparative separations of enantiomers.

The rotation angle/absorbance ratios C+ = alpha+/A+ and C- = a-/A-, determined via detection by a polarimeter and a photometer, were checked for the first time with reference to their use for on-line analysis during preparative separations. For this purpose, (+)-, (-)- and (+/-)-carvones were investigated by liquid chromatography (LC) on microcrystalline tribenzoylcellulose. It turned out that the ratios C+ and C- depend only slightly upon concentration (Table 1). Overlapped peaks of enantiomers were successfully submitted to computer deconvolution (e.g. Fig. 2, bottom). A procedure for on-line analysis during preparative LC is proposed.

Spirobipyridopyrans and indolinospiropyridopyrans: Synthesis, X-ray crystal structure, separation of enantiomers, and barriers to thermal cleavage of the C(sp(3))-O bond.

The novel chiral spirobipyridopyrans 1 and 2 were synthesized by the acid catalyzed aldol type condensation of 5-deoxypyridoxal with the appropriate ketone and subsequent reaction of the resulting pyrylium salt with base. The indolinospiropyridopyrans 3-5, which contain the modified B(6) unit, were prepared by aldol reaction of 5-deoxypyridoxal with 1,3,3-trimethyl-2-methylenindolines. Analytical separation of enantiomers was accomplished by low-pressure liquid chromatography (LPLC) on triacetylcellulose. The barriers to thermal racemization were determined by on-line measurements of the enriched enantiomers after LPLC. Gibbs energies of activation DeltaG superset, not equals for reversible cleavage of the C(spiro)-O bond in 1, 3, and 4 were in the range 103-108 kJ/mol. The lower limits of the barriers in 2 and 5 were estimated to be greater than 102 and 109 kJ/mol by attempted thermal racemizations. The increase of the barriers from 3 to 4 and 5 was explained by the influence of electron withdrawing groups, which reduce the stability of the ring-opened transition states to C(sp3)-O bond cleavage. Geometrical data from X-ray structure analysis showed that the angle [C3-C2-C3'] around the spiro carbon atom increases with elongation of the chain in the C3-C3' bridge. This angle widening is explained by a ring-strain effect, which is greater in the five-membered ring in the skeleton of 7 than in the six- and seven-membered rings of 1 and 2.

Inhibition of tubulin polymerization by 5,6-dihydroindolo[2,1-alpha]isoquinoline derivatives.

6-Alkyl-12-formyl-5,6-dihydroindolo[2,1-alpha]isoquinolines have been shown to inhibit the growth of human mammary carcinoma cells by an unknown mode of action. One of the possible molecular targets is the tubulin system which is involved in cell division. A number of 5,6-dihydroindolo[2,1-alpha]isoquinolines with methoxy or hydroxy groups in positions 3, 9, and/or 10 and various functional groups such as formyl, acetyl, cyano, alkylimino, and alkylamino in position 12 were synthesized and evaluated for both inhibition of tubulin polymerization and cytostatic activity in MDA-MB 231 and MCF-7 human breast cancer cells. In the tubulin polymerization assay, only hydroxy derivatives were active, whereas both the hydroxy derivatives and some of the methoxy compounds inhibited cell growth. In order to establish a correlation between the inhibition of tubulin polymerization and cytostatic activity in the hydroxy series, two of the most active racemates were separated into the enantiomers. In both assays, the relative potencies of the hydroxy derivatives were in a similar order. Highest activity was found for the (+)-isomers of 6-propyl- (6b) and 6-butyl-12-formyl-5,6-hydro-3,9-dihydroxyindolo[2,1-alpha]isoquino line (6c) with IC50 values of 11 +/- 0.4 and 3.1 +/- 0.4 microM, respectively, for the polymerization of tubulin at 37 degrees C (colchicine: 2.1 +/- 0.1 microM). The active hydroxy derivatives displaced 40-70% of [3H]colchicine from its binding site in the tubulin at concentrations 10-fold higher than that of colchicine. The data suggest that hydroxy-substituted indolo[2,1-alpha]isoquinolines bind to the colchicine-binding site and inhibit the polymerization of tubulin. This action can be assumed to be responsible for the cytostatic activity of the hydroxy derivatives and might also contribute to the antitumor effect of the corresponding methyl ethers.

Dibenzo[a,f]quinolizines: syntheses and cytostatic activity in estrogen-sensitive tumor cells.

A number of methoxy-substituted 7,11b,12,13-tetrahydro-6H-dibenzo-[a,f]quinolizines with short alkyl groups in position 6 or 12 were synthesized by the Bischler-Napieralski reaction using the appropriate starting material followed by a second ring closure reaction involving a base-generated benzyne intermediate. The methoxy functions in positions 2 or 3 and 9 were cleaved with BBr3 and the free hydroxy groups converted into the acetates. The enantiomers of two of these derivatives were separated by liquid chromatography on triacetylcellulose. Compounds with alkyl substituents bind strongly to the estrogen receptor except those with a cis-orientation at the central ring connection. The RBA values ranged from 2.2-10.8 (17 beta-estradiol: RBA = 100). There was no major difference in binding between the (+) and (-)-enantiomers. The 3,9-diacetoxy-6-alkyl derivatives also showed binding affinity for the progesterone receptor (RBA: 1.2-3.1). The 2,9-diacetoxydibenzoquinolizines trans-61 and -6m with ethyl and propyl respectively in position 12 strongly inhibited the growth of hormone-sensitive MCF-7 breast cancer cells at concentrations of 10(-6) M and higher but were inactive in hormone-independent MDA-MB 231 breast cancer cells. Preliminary tests with hormone-dependent MXT mouse mammary tumors as model showed that these compounds have also antineoplastic activity in vivo. Derivative trans-61 at a dose of 20 mg/kg body weight, administered 3 times/week, inhibited the growth of these tumors by 78% (tamoxifen: 76% inhibition). Studies on the estrogenic and antiestrogenic properties of these agents in mice revealed that they are mixed agonists/antagonists with strong antiestrogenic activity at low doses but significant estrogenic effects at higher doses.

Dibenzo[a,g]quinolizin-8-ones: synthesis, estrogen receptor affinities, and cytostatic activity.

A number of acetoxy-substituted dibenzo[a,g]quinolizin-8-ones were synthesized by the reaction of 1-oxoisoquinolines with substituted homophthalic acid anhydride. All of the derivatives with acetoxy groups in positions 3 and 10 bind to the estrogen receptor. Relative binding affinities (RBA) ranged from 1.8 to 5.6 (estradiol: RBA = 100) when the substituent at C-6 was a short alkyl group. Introduction of additional oxygen functions in the 2- and/or 11-position decreased binding affinities. Analyses of the enantiomers of 6-methyl (6b) and 6-ethyl (6c) derivatives revealed that the receptor binding is mainly due to one optical isomer (e.g. (-)-6b, 9.9; (+)-6b, 0.6). In hormone-sensitive human MCF-7 breast cancer cells, compounds with one acetoxy group in each aromatic ring strongly inhibited cellular growth. Despite marked differences in receptor affinity, the enantiomers displayed similar activities in this cell culture. In hormone-independent MDA-MB 231 mammary tumor cells, only a weak cytostatic effect was recorded at 10(-5) M. In the immature mouse uterine weight test, minimal estrogenic activity was observed. At higher doses, a significant anti-estrogenic effect became evident. It is assumed that the estrogen antagonism is responsible for the specific cytostatic effect in MCF-7 breast cancer cells.

6-Alkyl-12-formylindolo[2,1-a]isoquinolines. Syntheses, estrogen receptor binding affinities, and stereospecific cytostatic activity.

A number of 6-alkyl-12-formyl-5,6-dihydroindolol[2,1-a]isoquinolines were synthesized by the Bischler-Napieralski reaction from the respective 1-alkyl-2-(3-methoxyphenyl)ethylamines and bromo-substituted (methoxyphenyl)acetic acid chlorides followed by a second ring closure reaction involving a base-generated benzyne intermediate. The methoxy functions in positions 3 and 9 or 10 were cleaved with BBr3 and the free hydroxy groups converted into the acetates. The enantiomers of the most potent derivatives were separated by liquid chromatography on triacetylcellulose. All of the compounds tested bind to the calf uterine estrogen receptor. The relative binding affinities (RBA) ranged from 0.5 to 3.9 (17 beta-estradiol: RBA = 100) and were dependent on the position of the oxygen function in the indole moiety. The 3,10-diacetoxy derivatives showed higher RBA values than the corresponding 3,9-substituted tetracycles. There was no major difference in binding affinity between (+)- and (-)-enantiomers. Computer-assisted molecular modeling studies showed that the chiral carbon atom 6 of the indoloisoquinoline is likely to mimic the C-11 atom of estradiol. In the mouse uterine weight test, only the 3,10-diacetoxy series exhibited weak estrogenic activity at higher doses. The antiestrogenic effects found with all the compounds varied considerably. Maximum inhibition of estrone-stimulated uterine growth was found for the ethyl derivative 7d (80% with 250 micrograms/animal per day). All derivatives strongly inhibited the growth of human breast cancer cells in vitro. There was no significant difference between hormone-sensitive MCF-7 cells and hormone-independent MDA-MB 231 cells. Cytostatic activity was higher for the 3,9-substituted indoloisoquinolines than for the 3,10-analogues and dependent on the length of the alkyl group at C-6. The maximum effect was found with the butyl derivative 7g. When the enantiomers of the ethyl (7c), propyl (7e), and butyl derivative were studied, a strong difference in activity was observed between the stereoisomers. The IC50 values of the (+)-forms were usually only a tenth of those of the levorotatory isomers. Maximum cytostatic activity was found with (+)-7g: 85% inhibition at 1 x 10(-7) M in MCF-7 cells and 94% inhibition at 2.5 x 10(-7) M in MDA-MB 231 cells. This stereospecificity indicates a selective action on a biochemical target. Since no interaction with DNA was observed, the precise mode of action still remains to be elucidated.

Synthesis and aromatase inhibition of 3-cycloalkyl-substituted 3-(4-aminophenyl)piperidine-2,6-diones.

The synthesis of 3-cycloalkyl-substituted 3-(4-aminophenyl)piperidine-2,6-diones is described [cyclopentyl (1), cyclohexyl (2)]. The enantiomers of 2 were separated either by using HPLC on optically active sorbent or by crystallization of the brucine salt of the phthalamic acid of 2. The absolute configuration of the (+)- and (-)-enantiomers of 2 were assigned as S and R, respectively, by comparing the CD spectra to those of the enantiomers of aminoglutethimide (AG, 3-(4-aminophenyl)-3-ethylpiperidine-2,6-dione). The compounds were tested in vitro for inhibition of human placental aromatase, the cytochrome P450-dependent enzyme which is responsible for the conversion of androgens to estrogens. Compounds 1 and 2 inhibited aromatase by 50% at 1.2 and 0.3 microM, respectively (IC50 AG = 37 microM). According to the findings with AG, the (+)-enantiomer of 2 was responsible for the inhibitory activity, being a 240-fold more potent aromatase inhibitor in vitro than racemic AG. On the other hand, (+)-2 displayed a strongly reduced inhibition of desmolase (cholesterol side-chain cleavage enzyme) compared to AG (relative activity = 0.3). Thus (+)-2 is of interest as a potential drug for the treatment of estrogen-dependent diseases, e.g. mammary tumors.

[1,2-Bis(2-hydroxyphenyl)ethylenediamine]dichloroplatinum(II), a new compound for the therapy of ovarian cancer. II. Synthesis and preliminary testing of the enantiomeric complexes.

The enantiomeric [1,2-bis(2-hydroxyphenyl)-ethylenediamine]dichloroplatinum(II) complexes were synthesized and their configuration assessed. A preliminary test in the cisplatin-resistant human NIH:OVCAR-3 ovarian cancer cell line, which was previously characterized by its sensitivity against several therapeutically used drugs, showed that both enantiomers produce cytocidal effects in a concentration of 2.5 microM. A difference between the enantiomers became evident from the faster onset of cytocidal activity of the S,S-configurated compound.

[1,2-Bis(2-hydroxyphenyl)ethylenediamine]dichloroplatinum(II), a new compound for the therapy of ovarian cancer. III. Detailed evaluation of the antitumor activity of the enantiomeric complexes on the human NIH:OVCAR-3 ovarian cancer cell line.

The stereoisomeric [1,2-bis(2-hydroxyphenyl)ethylenediamine]dichloroplatinum(II) complexes were thoroughly tested on the cisplatin-resistant human NIH:OVCAR-3 ovarian cancer cell line. The racemate and its enantiomers produced cytocidal effects at a concentration of 2.5 microM (incubation time 256 h). The meso form, however, was merely cytostatically active. Differences between the enantiomers became evident after a short drug incubation time (1 h) followed by an incubation in drug-free medium (243 h). The S,S-configurated enantiomer (-)-3-PtCl2 proved to be the most active compound. To achieve cytocidal effects concentrations of 2.5-5.0 microM and incubation times of about 3 h were necessary for (-)-3-PtCl2. This compound is also sufficiently stable under test conditions as shown by the preincubation in cell-free medium for 3 h. These results and the augmentation of its antitumor activity by buthionine sulfoximine recommend the further preclinical development of (-)-3-PtCl2 for clinical use.

New aromatase inhibitors. Synthesis and biological activity of pyridyl-substituted tetralone derivatives.

The (E)-2-(4-pyridylmethylene)-1-tetralones 1-7 (1, H; 2, 5-OCH3; 3, 6-OCH3; 4, 7-OCH3; 5, 5-OH; 6, 6-OH; 7, 7-OH) were obtained by aldol condensation of the corresponding 1-tetralones with 4-pyridinecarboxaldehyde, and in the case of the OH compounds 5 and 7 subsequent ether cleavage of the OCH3-substituted 2-(4-pyridylmethylene)-1-tetralones. Catalytic hydrogenation of 1-4 gave the 2-(4-pyridylmethyl)-1-tetralones 8-11 (8, H; 9, 5-OCH3; 10, 6-OCH3; 11, 7-OCH3). Subsequent ether cleavage of 9-11 led to the corresponding OH compounds 12-14 (12, 5-OH; 13, 6-OH; 14, 7-OH). The enantiomers of 11 and 12 were separated semipreparatively by HPLC on triacetylcellulose. All compounds (1-14) showed an inhibition of human placental aromatase exhibiting relative potencies from 2.2 to 213 [compounds 6 and (+)-12, respectively; aromatase inhibitory potency of aminoglutethimide (AG) = 1]. The compounds exhibited no or only a weak inhibition of desmolase [cholesterol side chain cleavage enzyme; maximum activity shown by 12, 23% inhibition (25 microM); AG, 53% inhibition (25 microM)]. In vivo, however, the compounds were not superior to AG as far as the reduction of the plasma estradiol concentration and the mammary carcinoma (MC) inhibiting properties are concerned (PMSG-primed SD rats as well as DMBA-induced MC of the SD rat, pre- and postmenopausal experiments, and the transplantable MXT-MC of the BD2F1 mouse). This is due to a fast decrease of the plasma E2 concentration inhibiting effect as could be shown by a kinetic experiment. In addition, select compounds inhibited rat ovarian aromatase much less than human placental aromatase (12, factor of 10). Estrogenic effects as a cause for the poor in vivo activity of the test compounds could be excluded, since they did not show affinity for the estrogen receptor.

Differential potency of atropisomers of polychlorinated biphenyls on cytochrome P450 induction and uroporphyrin accumulation in the chick embryo hepatocyte culture.

The atropisomers of 2,2',3,4,6-pentachlorobiphenyl (PeCB), 2,2',3,4,4',6-hexachlorobiphenyl (HeCB), and 2,2',3,3',4,4',6,6'-octachlorobiphenyl (OCB) were studied in the chick embryo hepatocyte culture to determine if chirality plays a role in the recognition events associated with the induction of cytochromes P450 and the accumulation of uroporphyrin (URO). Concentration-related induction of cytochrome P450 content, ethoxyresorufin-O-deethylase (EROD) and benzphetamine N-demethylase (BPDM) activities were measured. The rank order of potency for total cytochrome P450 induction was HeCB greater than OCB greater than or equal to PeCB. The (+)- and (-)-enantiomers of PeCB and OCB were of equal potencies as inducers of cytochromes P450, whereas the (+)-HeCB was greater than the (-)-HeCB. HeCB was a much more potent inducer of EROD activity than was either PeCB or OCB. EROD activity was induced to a much greater extent by the (+)-enantiomers of all compounds, with the (-)-enantiomers of PeCB and OCB being inactive. BPDM activity was induced by all three compounds in the order of OCB greater than or equal to HeCB greater than PeCB. The (-)-enantiomers were more potent inducers of BPDM activities than were the (+)-enantiomers, except for HeCB, in which the (+)- was more potent than the (-)-enantiomer. Analysis of porphyrin accumulation in cultures treated with delta-aminolevulinic acid revealed that (+)-HeCB caused the greatest percent URO accumulation, which also correlated with the greatest increase in EROD activity. All other enantiomers caused up to 47% URO accumulation, which did not correlate with an increase in EROD activity.

Aqua[1-(2,6-dichloro-4-hydroxyphenyl)-2- phenylethylenediamine](sulfato)platinum-(II) complexes with variable substituents in the 2-phenyl ring. 1. Synthesis and antitumor and estrogenic properties.

Erythro- and threo-configurated aqua[1-(2,6-dichloro-4-hydroxyphenyl)-2- phenylethylenediamine](sulfato)platinum(II) complexes with variable substituents in the 2-phenyl ring (2-PtSO4 to 9-PtSO4: H, 4-F, 3-OH, 4-OH, 2,6-F2, 2,6-Cl2, 2-F/4-OH, 2-Cl/4-OH) were synthesized and tested for estrogenic and antitumor activities. The ligands were obtained by a three-step reaction. The stilbenes were reacted with a mixture of IN3 and NaN3 to yield the respective 1,2-diazido-1,2-diphenylethanes. The subsequent reduction with LiAlH4 led to the corresponding 1,2-diphenyl-ethylenediamines. The (sulfato)platinum(II) complexes were synthesized by reaction of Ag2SO4 with the diiodo complexes, which had been obtained by coordination of the diamines with K2PtI4. Two complexes, erythro-8-PtSO4 and erythro-9-PtSO4, possess antitumor and estrogenic effects and are therefore of interest for the therapy of breast cancer.

Tumor-inhibiting [1,2-bis(fluorophenyl)ethylenediamine]platinum(II) complexes. V. Synthesis and evaluation of enantiomeric [1,2-bis-(4-fluorophenyl)ethylenediamine]dichloroplatinum(II) complexes.

The enantiomeric [1,2-bis(4-fluorophenyl)ethylenediamine]dichloroplatinum(II) complexes were synthesized and tested on the hormone-sensitive human MCF7 breast cancer cell line and on the P388 leukemia of the mouse. They showed a strong and comparable activity on both tumor models.

Chiral effects in the induction of drug-metabolizing enzymes using synthetic atropisomers of polychlorinated biphenyls (PCBs).

Atropisomers of the polychlorinated biphenyls 2,2',3,4,4',6-hexachlorobiphenyl (II) and 2,2',3,3',4,4',6,6'-octachlorobiphenyl (III), stable to racemization under physiological conditions, were administered to immature male Sprague-Dawley rats. The racemic hexachlorobiphenyl (II) was found to be a potent (phenobarbital-type) inducer, whereas (+)-II and (-)-II, administered at 100 mumol/kg, showed clearly differing potencies as inducers with (+)-II enhancing aminopyrine N-demethylase, aldrin epoxidase and cytochrome P-450 content more potently than (-)-II. In contrast, the racemic octachlorobiphenyl (III) and its individual enantiomers were only weak phenobarbital-type inducers of cytochrome P-450, and the enantiomers of III were equally (weakly) potent. Separate studies conducted to investigate pharmacokinetic influences on the differential potency of the enantiomers of II showed that after 5 days the concentration of (+)-II in the liver was twice as high as that of its antipode. Therefore, enantioselectivity in disposition as well as in recognition may be responsible for the differential potency seen.

[The occurrence of a reductase of delta2-carboxylic acids in Clostridium kluyveri with a stereospecificity different from that of butyryl-CoA dehydrogenase (author's transl)]. / Uber des Vorkommen einer Reduktase von delta2-Carbonsäuren in Clostridium kluyveri mit einer von der Butyryl-Coa-dehydrogenase verschiedenen Stereospezifität

A Clostridia strain (R-strain) which hydrogenates tiglinate (1b) and alpha-methylcinnamate (1c) in the presence of hydrogenase gas in 2H2O to (2R, 3S)2-methyl-[2,3-2H]butyrate (5b, H = 2H) and (alphaR, betaR)alpha-methyl[alpha,beta-2H]dihydrocinnamate (5c, H = 2H), respectively, was isolated. The configuration at C-3 was determined by 1H-NMR spectroscopy in the presence of Eu(fod)3. The stereochemistry of this hydrogenation is the mirror image of that which has been determined with intact cells of another strain of Clostridium kluyveri (S-strain). In the presence of hydrogen gas, the R-strain hydrogenates crotonate in 2H2O to butyrate with the following deuterium distribution: C-2, 1.85; C-3, 1.35; and C-4, 0.63 deuterium atoms. Crotonate seems to be the substrate of two reductases with sterically different actions. Tiglinate (1b) and alpha-methylcinnamate, however, are hydrogenated only by that reductase which is different from the butyryl-CoA dehydrogenase.