Optical Rotatory Dispersion Curves Research Articles

Total synthesis of ( - )-trypargine.

The total synthesis of (±)-trypargine (2) was accomplished to confirm the proposed structure, 1-(3'-guanidinopropyl)-1, 2, 3, 4-tetrahydro-β-carboline. Optically active (-)-trypargine (2a) and its enantiomer (2b) were obtained by the optical resolution of the racemate. The stereochemistry at C-1 is discussed on the basis of the optical rotatory dispersion and circular dichroism curves.

Physical Characterization of Amylose‐Fatty Acid Complexes in Starch Granules and in Solution

AbstractPrevious differential scanning calorimetry studies of native starch have shown an endotherm at ∼ 100°C on heating, which is attributed to melting of an amylose‐lipid complex. In the present work we have shown that this transition is fully reversible (ΔH ≈ 0.4 ± 0.1 cal g−1 on heating and cooling) and displays substantial thermal hysteresis (Tm≈76°C on cooling). On removal of lipid by extraction with methanol the transition is lost, but re‐appears on addition of sodium palmitate to de‐fatted granules. Closely similar thermal behaviour, including hysteresis, is observed on addition of palmitate to amylose. Further evidence of complex formation between amylose and palmitate is the almost total disappearance of high resolution 1H n.m.r. signal, indicating loss of conformational mobility by the polysaccharide chain. Formation of the complex is also accompanied by a large reduction in optical activity. Using an established correlation between D‐line optical rotation and the dihedral angles between adjacent residues we have compared the observed optical rotation with values calculated for specific ordered structures of amylose. The measured optical rotation values indicate adoption in solution of a novel right‐handed V‐amylose structure (calculated [α] D=104°; found = 100±5°) rather than the expected left‐handed form characterized in the solid state (calculated [α] D=157°). Analysis of optical rotatory dispersion curves shows that in each case the changes in optical rotation on complex formation arise predominantly from changes in the intensity of the known polysaccharide backbone transition at 161 nm.

An empirical correlation between structure and optical activity in a series of labdane diterpenoids

On the basis of the results of an analysis of the optical rotatory dispersion curves and a consideration of possible conformations of labdane diterpenoids, the conclusion has been drawn that labd-8(17)-ene derivatives with a 13E double bond or a voluminous substituent in the side chain do not obey Garman's additive scheme, and when there are no asymmetric centers in the side chain they have more negative values of the molecular optical rotation than is preducted by this scheme.

An Application of the Extended Principal Component Analysis to Circular Dichroism and Optical Rotatory Dispersion. A Case of Poly(α-l-glutamic acid) in the Helix-Coil Transition Region

Abstract The extended principal-component-analysis (PCA) method has been applied to circular dichroism (CD) and optical rotatory dispersion (ORD). The validity of this method has been examined with ideal binary and ternary equilibrium systems, for which the data CD spectra and ORD curves were computer-generated. Satisfactory results were obtained for these multicomponent optically active systems. As an example, the ultraviolet CD spectra of poly(α-l-glutamic acid) in the pH-induced helix-coil transition region were analyzed with the PCA procedure. By the extended PCA method, the pure CD spectra for both helix and random-coil conformations and the helix fractions in the transition region were determined from eight experimentally obtained CD spectra. By introducing an empirical parameter α into the Henderson-Hasselbalch equation, the helix-coil transition curve was reproduced reasonably well.

Studies on the constituents of Chloranthus spp. III. Six sesquiterpenes from Chloranthus japonicus.

Six sesquiterpene lactones (I-VI) were isolated and characterized as constituents of Chloranthus japonicus (Chloranthaceae). The lactones chloranthalactone A-E (I-V) were found to be lindenane derivatives, and the lactone VI was identified as atractylenolide III. The structure of chloranthalactone C (III) was determined by X-ray crystallographic analysis of a crystal of III in conjunction with the negative Cotton effect in the optical rotatory dispersion (ORD) curve and negative circular dichroism curve of the ketoalcohol (XII) prepared from III. The stereostructures of chloranthalactone A and B (I and II) were deduced from the ORD curves of the degradation products (VII and X). The cytotoxicities of these lactones against mouse lymphosarcoma L-5178Y cells were determined in comparison with that of helenalin, and they were found to show moderate cytotoxic effects.

Optical rotatory dispersion and vacuum ultraviolet circular dichroism of poly[(R)‐oxypropylene

AbstractThe circular dichroism (CD) spectrum of poly[(R)‐oxypropylene] in a number of solvents has been measured in the vacuum ultraviolet region. Two CD bands were measured for cyclohexane, acetonitrile, and trifluoroethanol solutions. The CD spectrum was extended to 140 nm and three bands were measured in a 1,1,1,3,3,3‐hexafluoro‐2‐propanol solution. The similarity of these four CD spectra in sign, shape, and intensity confirm that poly[(R)‐oxypropylene] has similar conformations in all solvents studied, even though the optical rotatory dispersion (ORD) in the visible region is positive for the cyclohexane solution but negative for the alcohol solutions. A Kronig–Kramers transform of the two CD bands observed for the cyclohexane solution accounts for the observed positive ORD spectrum. In contrast, a third large and negative CD band centered below 160 nm is necessary to account for the negative ORD spectra observed for the alcohol solutions. Apparently the anomalous sign variation of the ORD curves observed in the visible region is due to subtle changes in the interplay of a large number of CD bands. Solvent interaction, observed as a blue shift of the first two CD bands for the alcohol solutions, could produce the subtle changes necessary to change the sign of the ORD curve in the visible region. The first two CD bands of poly[(R)‐oxypropylene] are tentatively assigned as nσ* and the third as an n3s.

Optically Active Monoacetyldiacylglycerols from Stauntonia hexaphylla Seed Oil

Optically active monoacetyldiacylglycerols were isolated from the Stauntonia hexaphylla seed oil. The hydrogenated Stauntonia monoacetyldiacylglycerols gave a plain, negative optical rotatory dispersion curve. Comparison of the triacylglycerols with those of known configuration in the optical rotatory behavior showed that all Stauntonia monoacetyldiacylglycerols were essentially (S) -3-acetyl-1, 2-diacylglycerol. The constituent acids, other than acetic, of the triacylglycerols were ordinary long-chain fatty acids. Octadecenoic and octadecadienoic acids were present in abundance in the 2-position.

Synthesis of C-substituted triazoles, isoxazoles, and pyrazoles by 1,3-dipolar cycloaddition to acetylenic sugars

Addition of phenyl azide to 3,5-di- O-acetyl-6,7-dideoxy-1,2- O-isopropylidene-β- l- idio-hept-6-ynofuranose ( 1) and subsequent saponification gave a 4-substituted 1-phenyl-1,2,3-triazole derivative ( 3) whose optical rotatory dispersion (o.r.d.) curve was positive. The α- d- gluco analog ( 5) of 1 similarly gave the 5-epimer ( 7) of 3; its o.r.d. curve was negative. Both 3 and 7 were degraded to the known 1-phenyl-1,2,3-triazole-4-carboxaldehyde. Similarly, addition of 2,4,6-trimethylbenzonitrile N-oxide to 1 or 5 gave the corresponding, crystalline 3-mesitylisoxazoles as single products; 13C-n.m.r. spectroscopy was used to establish the orientation of addition. Related 3-mesitylisoxazoles ( 11 and 13) were obtained from 1,2:3,4-di- O-isopropylidene- d- glycero-α- d-galacto -oct-7-ynopyranose ( 10) and its l- glycero 6-epimer ( 12), respectively; 11 showed the expected, large levorotation, and the 6-epimer 13 was also levorotatory. Benzonitrile ( N-phenyl)imine, prepared in situ from 1-(α-chlorobenzylidene)-2-phenylhydrazine and base, did not react with 10 (or its 6-epimer 12), but did react with the 6-keto analog to give a 5-substituted 1,3-diphenyl-1,2-diazole.

LSD and phenithylamine hallucinogens: New structural analogy and implications for receptor geometry

The hallucinogen analog trans -2-(2,5-dimethoxy-4-methylphenyl)-cyclopropylamine (DMCPA) was resolved into its two optical isomers. Examination of selected behavioral profiles in mice and cats clearly showed that the levorotatory isomer of DMCPA possesses stereoselective activity when compared with the dextro isomer. The results parallel those obtained using the isomers of the known hallucinogen, DOM (STP) in the same animal models. Comparison of the optical rotatory dispersion (ORD) curves for the N-(5-bromosalicylidene) derivatives of DMCPA and trans -2-phenylcyclopropylamine (tranylcypromine) of known absolute configuration established the configuration of DMCPA to be (-)-1R,2S. This stereoselective activity and proof of absolute configuration lend strong support to a new model of the hallucinogen receptor. The proposed model suggests possible structural similarities between LSD and phenethylamine hallucinogens.

Stereochemical studies of the pyruvate kinase reaction with (Z)- and (E)-phosphoenol-alpha-ketobutyrate.

(Z)-and (E)-phosphoenol-2-ketobutyrate were synthesized. [3-2H]-2-Ketobutyrates were formed from both isomers in the pyruvate kinase reaction in 2H2O and were converted to chiral propionates. Authentic (2S)-[2-2H]propionic acid was also prepared, and the optical rotatory dispersion curves of the propionates were compared. The rotation compared with standard propionate at 240 nm of sodium (2R)-[2-2H]propionate from the Z isomer was 47% (i.e., 53% was RS), and of (2S)-[2-2H]propionate from the E isomer was 29% (i.e., 71% was RS). Protonation at C-3 of the 2 si, 3 re face of the pseudosubstrates would have yielded (2R)- and (2S)-[2-2H]propionates from the Z and E analogues, respectively. An explanation offered for the nonstereoselective protonation that occurred is dissociation of the enol from the enzyme and subsequent random protonation in solution.

The absolute configuration of the enantiomers of glutethimide and aminoglutethimide.

Aminoglutethimide (Elipten¿ CIBA) was resolved into the optical antipodes I and II. The endocrinological properties and the absolute configuration of both enantiomers I and II were determined. Most of the steroidal synthesis inhibition was found in the (+) enantiomer II. On the basis of circular dichroism, the R-configuration was assigned to the (+) enantiomer II.

Stereochemistry of the reaction catalyzed by mevaldate reductase

3 RS-[5-D 1]Mevalonate was prepared by the reduction of RS-mevaldate with [4 R-4-D 1]NADH and mevaldate reductase and was resolved enzymically into the 3 R- and 3 S-isomers. Spectropolarimetric measurements gave nearly mirror-image optical rotatory dispersion curves with a minimum and maximum at 240 nm and a negative and positive Cotton effect, λ 0 being at 227 nm, for the 3 R- and 3 S-lactone, respectively. Since the H-atoms at C-5 of mevalonolactone form a virtual ABX 2 system in nmr, the chemical shifts of the equatorial and axial H-atoms being at δ 4.33 and 4.58, respectively, it was possible to show by nmr that the two [5-D 1]-lactones were diastereoisomers, both having the 5 R absolute configuration. This conclusion was confirmed by the finding that speciments of 3-methyl[5-D 1]pent-2-eno-5-lactone made by the dehydration of 3 S-[5-D 1]mevalonolactone and of 3 RS-[5-D 1]mevalonolactone had identical optical activities and of the same sign. The implications of the observations and a correlation between the stereochemistry of the reactions catalyzed by mevaldate reductase and 3-hydroxy-3-methylglutaryl-CoA reductase are discussed.

Syntheses of Poly(S-benzyl D- and L-penicillamines) and Their Secondary Structures

Poly(S-benzyl D- and L-penicillamines) were prepared from the corresponding N-carboxyanhydrides (NCA). These polymers were soluble in alkyl halides, such as chloroform and methylene dichloride, but insoluble in dichloroacetic acid (DCA) and trifluoroacetic acid (TFA). Judging from the results obtained by a study of the infrared absorption (IR) spectra and X-ray photographs, polymers are in the ω-helical structure in the solid state. The results of the optical rotatory dispersion (ORD) and the circular dichroism (CD) in chloroform suggest that these polymers have the ω-helical structure and their helical senses are reversed. By adding TFA to the chloroform solution of these polymers, both ORD and CD curves are markedly changed from the ω-helical structure to the β-structure. The intrinsic viscosity and the flotation data indicated that the polymer exists in the intermolecular β-structure in a chloroform—TFA mixture.

Symmetry rules for chiral aliphatic amines and their salts

1. The sign of the Cotton effect in the circular dichroism (CD) spectra of secondary cyclic amines and the sign of the optical rotatory dispersion (ORD) curve of their salts obey the rule of squares. 2. The sign of the ORD curve of salts of tertiary cyclic amines obeys a sector rule consisting of six sign-determining regions. 3. The sign of the Cotton effect in the CD spectra of tertiary cyclic amines obeys a sector rule consisting of 12 sign-determining regions.

Asymmetric addition of thiol to diene polymer in the presence of optically active amines as catalyst

The asymmetric addition reaction of thiolacetic acid or benzylmercaptan to diene polymer (natural rubber, cis- and trans-1,4-polyisoprene, cis-1,4-polybutadiene, various styrenebutadiene copolymers and alternating acrylonitrile-butadiene copolymer) by optically active catalysts such as d-bornylamine ([α] d−45.2°), l-aspartic diethyl ester (−11.2°), l-aspartic dibutyl ester (−5.3°) were carried out in benzene at room temperature to 90°C. The optically active polymers were obtained from natural rubber and cis-1,4- and trans-1,4-polyisoprene, but were not obtained from cis-1,4-polybutadiene, styrene-butadiene copolymers, and butadiene-acrylonitrile copolymer. The [ α] 25 D value of optically active derivatives was −0.1° ∼ −1.0° (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation.

Conformational states of methylamides of N-acetyl α-amino acids and their N-methyl derivatives V. Ultraviolet spectra and circular dichroism and optical rotatory dispersion curves

1. The UV spectra and CD and ORD curves of methylamides and dimethylamides of acetylamino acids have been studied in polar and nonpolar media.

Reaction of thiol to diene polymer in the presence of various catalysts

The addition reaction of benzylmercaptan to diene polymer (natural rubber, and cis-1,4-polyisoprene) by various optically active catalysts such as d-camphorsulphonic acid, d-percamphoric acid, and active-amylalcoholate (sodium and barium) were carried out in benzene or anisole at room temperature to 100°C. The optically active adduct polymer was only obtained from the reaction of benzylmercaptan to natural rubber and cis-1,4-polyisoprene by active-amylalcoholate (barium), but was not obtained by the other catalysts. The [ α] 25 value of optically active adduct polymer was −0·1°C∼−0·6°C (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation. The reaction of benzylmercaptan to cis-1,4-polybutadiene, various styrene-butadiene copolymers, and alternating butadiene-acrylonitrile copolymer were carried out, but the optically active adduct polymers were not obtained by these catalysts.

Characterisation of the products from the oxidation of progesterone with osmium tetroxide

The nature of the compounds resulting from treatment of progesterone and 6β-hydroxy-4-pregnene-3,20-dione with hydrogen peroxide and catalytic quantities of osmium tetroxide was investigated. This reagent gives mixtures of 4,5-cis-glycols and the structures were assigned using kinetic dehydration studies, optical rotatory dispersion curves and nuclear magnetic resonance spectra.

Induction of optical activity in a nematic mesophase by l-menthol. Optical properties of liquid crystal mixtures

The helical twisting power of l-menthol in a nematic solvent (MBBA) has been measured by means of induced optical activity and circular dichroism. The optical rotatory dispersion curve is extremely broadened corresponding to a widened region of total reflection. The induced twist sharply increases with concentration resulting in a maximum value prior to the breakdown of liquid crystal structure. These results are in excellent agreement with the predictions of the molecular theory of Goossens.

Conformational behavior of a gel-forming (1→3)-β- D-glucan in alkaline solution

Conformational behavior of a gel-forming (1→3)-β- D-glucan in sodium hydroxide solution was studied by optical rotatory dispersion, viscosity, and flow birefringence measurements, the alkali concentration being changed from 5m M up to 4.8 M. In the wavelength range studied (230–500nm), optical rotatory dispersion curves were anomalous, except the curve obtained with 4.8 M sodium hydroxide. At longer wavelengths and low alkali concentration, the sign of rotation angle was positive, and at shorter wavelengths, it decreased sharply resulting in a broad maximum near 265nm. The angle of rotation at a given wavelength fell sharply with alkali concentration in the range of 0.19–0.24 M. These changes were reversible when the sodium hydroxide concentration was varied. Intrinsic viscosity and flow birefringence also showed large changes corresponding to the rotation angle change. These observations suggest that, in solutions of low sodium hydroxide concentration, the (1→3)-β- D-glucan takes an ordered conformation, whereas it practically behaves as a random coil at high concentration, a conformational transition occurring in the region between 0.19 and 0.24 M. When sodium hydroxide was replaced with lithium hydroxide, a similar dependence of the optical rotation and the viscosity on the alkali concentration was observed.