Group-theoretical Foundations for the Concept of Mandalas as Diagrammatical Expressions for Characterizing Symmetries of Stereoisomers

Group-theoretical foundations for the concept of mandalas have been formulated algebraically and diagrammatically in order to reinforce the spread of the unit-subduced-cycle-index (USCI) approach (S. Fujita, Symmetry and Combinatorial Enumeration in Chemistry, Springer-Verlag, Berlin-Heidelberg, 1991). Thus, after the introducton of right coset representations (RCR) (H\)G and left coset representations (LCR) G(/H) for the group G and its subgroup H, a regular body of G-symmetry is defined as a diagrammatical expression for a right regular representation (C ₁\)G, which is an extreme case of RCRs. The |G| substitution positions of the regular body as a reference are numbered in accord with the numbering of the elements of G and segmented into |G|/|H| of H-segments, which are governed by the RCR (H\)G. By regarding each H-segment as a substitution position, the H-segmented regular body is reduced into a reduced regular body, which can be regarded as a secondary skeleton for generating a molecule. The reference regular body (or H-segmented one) is operated by every symmetry operations of G to generate regular bodies (or H-segmented ones), which are placed on the vertices of a hypothetical regular body of G-symmetry. The resulting diagram (a nested regular body) is called a mandala (or a reduced mandala), which is a diagrammatical expression for specifying the G-symmetry of a molecule. The effect of a K-subduction on the regular bodies of a mandala (or a reduced mandala) results in the K-assemblage of the mandala (or the reduced mandala), where the resulting K-assemblies governed by the LCR G(/K) construct a |G|/|K|-membered orbit, which corresponds to a molecule of K-symmetry. The sphericity of the RCR (or the LCR) is used to characterize symmetrical properties of substitution positions and those of stereoisomers. The fixed-point vector for each mandala (or reduced mandala) in terms of row view and the number of fixed points of K-assembled mandalas (or K-assembled reduced mandalas) in terms of column view are compared to accomplish combinatorial enumeration of stereoisomers. The relationship between a mandala and a reordered multiplication table is discussed.     

Zinc and cobalt complexes with (2-carboxyphenoxy) acetic acid ligand: syntheses,structures, fluorescent and magnetic properties

Four binary compounds, [Zn(cpa)(H₂O)₃] (1), [Co(cpa)(H₂O)₃] (2), [Zn(cpa)(H₂O)]_n, (3) and [Co(cpa)(H₂O)]_n (4) (H₂cpa = (2-carboxyphenoxy)acetic acid), have been synthesized and structurally characterized. In mononuclear 1 or 2, the metal ion (Zn^II for 1 and Co^II for 2) is surrounded by three water molecules and one tridentate chelate cpa^2? in a distorted octahedral geometry, while in 3 or 4, the central metal ion (Zn^II for 3 and Co^II for 4) is located in a deformed square–pyramid formed by one water and two cpa^2?. Each cpa^2? is chelate bridging μ₂ coordination and forms a 1-D zigzag chain structure 2 or 3. The different synthesis conditions for 1–4 have been carefully discussed. The solid-state fluorescence measurements for 1 and 3 together with magnetic properties for 4 also have been investigated.     

2‐Hydroxy‐1,2,3,6‐tetrahydro‐azulen‐6‐carboxylic Acid Ethyl Ester—A Novel Precursor for a New Class of Liquid Crystalline Materials

A novel approach for the syntheses of carbene adduct 4 is reported. A ring-enlargement strategy was employed for the synthesis of precursors 5 and 6 and established the mechanism of the formation of azulene derivative 6. Synthesis of target precursor 13, a novel precursor for the synthesis of new mesogenic materials, and its various halogenated derivatives (14–16) was carried out.     

Ab Initio Study of the Various Pathways of the Decomposition ([2+2]elimination) of 2-Chloroethyltrichlorosilane

Abstract

The decomposition of 2-chloroethyltrichlorosilane (1) to ethylene-tetrachlorosilane (2), hydrogen chloride-ethylenetrichlorosilane (3), and ethylenechloride-trichlorosilane (4) was investigated using ab initio Molecular Orbital (MO) and Density Functional Theory (DFT). Study on the HF/6-31G level of theory revealed that the required energy for the decomposition of compound 1 to 2, 3, and 4 is 59.86, 101.13, and 63.29 kcal mol^?, respectively. MP2/6-31G*//HF/6-31G* calculated barrier height for the decomposition of compound 1 to 2, 3, and 4 is 60.59, 94.04, and 66.91 kcal mol^?1, respectively. Also, B3LYP/6-31G*//HF/6-31G* results indicate that the barrier height for the decomposition of compound 1 to 2, 3, and 4 is 51.71, 85.38, and 53.74 kcal mol^?1, respectively. Among the three methods, which have been used to calculate the barrier height of the decomposition of compound 1 to 2–4, B3LYP/6-31G**//HF/6-31G** is in good agreement with the reported experimental data. Contrary to the previously evaluated experimental values for the decomposition of compoun 1 to 3 and 4, all three methods predict a higher energy barrier for these reactions.     

An Ab Initio Study of Conformational Energies in Dioxo-, Trioxo-, and Tetroxo-Dithianes

Ab initio Hartree–Fock calculations at the HF/6-31G* level of theory for geometry optimization and the MP2/6-31G*//HF/6-31G* and B3LYP/6-311G(2df,p)//HF/6-31G* levels for a single point total energy calculation are reported for the important energy-minimum conformations of 1,1-dioxo-thiane (2), 1,1-dioxo-1,2-dithiane (3), 1,1-dioxo-1,3-dithiane (4), 1,1-dioxo-1,4-dithiane (5), 1,1,2-trioxo-1,2-dithiane (6), 1,1,3-trioxo-1,3-dithiane (7), 1,1,4-trioxo-1,4-dithiane (8), 1,1,2,2-tetroxo-1,2-dithiane (9), 1,1,3,3-tetroxo-1,3-dithiane (10), and 1,1,4,4-tetroxo-1,4-dithiane (11). According to the MP2/6-31G*//HF/6-31G* calculations, compound 5 is more stable than 3 and 4 by 7.8 and 8.9 kJ mol^?1, respectively. The axial geometries of 6 and 8 are more stable than the equatorial forms by 21.4 and 19.1 kJ mol^?1, respectively, but the equatorial form of 7 is 4.1 kJ mol^?1 more stable than the axial geometry. Compound 11 is more stable than 9 and 10 by 49.3 and 31.0 kJ mol^?1, respectively.     

Zur Reaktivität 4,5-ungesättigter 3-Oxoalkannitrile gegenüberMichael-Acceptoren

The 3-oxonitrile1 as well as the 2-benzylidene-3-oxonitrile4 on reaction with benzylidenemalononitrile or malononitrile, respectively, afford 2-amino-4H-pyran derivative3 in high yield. In contrast, reactions of1 and4 with ethyl benzylidenecyanoacetate (6) or ethylcyanoacetate, respectively, predominantly lead to a carbocyclic compound, which is also obtained as main product on attempted condensation of1 with benzaldehyde. Based on spectroscopic data, structure5 is proposed for the novel compound; its formation is interpreted in terms of piperidine-catalysed addition of1 to4 and subsequent intramolecularMichael addition. Reaction mechanisms for the conversion of1 and6 or4 and ethylcyanoacetate to5 are discussed.

Herrn Univ. Prof. Dr. Dr. h c.K. Kratzl zum 70. Geburtstag gewidmet.     

ORGANISCHE PHOSPHORVERBINDUNGEN 80 HERSTELLUNG VON TRIAZOLYLMETHYL-PHOSPHONATEN UND VON TRIAZOLYL-METHYLPHOSPHONIUMSALZEN UND DEREN VERWENDUNG IN DER WITTIG-HORNER REAKTION

Abstract

Attempts to prepare 1H-1,2,4-triazol-1-ylmethylphosphonates (4 and 5) by a Mannichtype reaction or by transesterification of 1-hydroxymethyl-1H-1,2,4-triazol 1 with tertiary phosphites failed. On the other hand 4 and 5 are obtained by a Michaelis-Becker reaction from 1-chloromethyl-1H-1,2,4-triazol 3 and sodium phosphites in high yield. The Michaelis-Arbuzov reaction is less suited for the preparation of 4 and 5. 3 is obtained in good yield as a water clear liquid, b.p. 52–54°C/0.2 torr, from the interaction of 1 with thionyl chloride followed by treatment with a base. On standing at 0° or 20°C it decomposes within hours and yields the unsymmetrical methylen-bis(triazol) 3a in addition to other products. However an acetonitrile solution of 3 is stable for months. Heating this solution with tertiary phosphines gives triazolylsubstituted phosphoniumsalts 6 to 8. The Wittig-Horner reaction with 4 to 6 gives the olefinically substituted triazols 9–12 as a Z/E mixture in high yield. Alkylation of 4 with methyl-and ethyl iodide gives the corresponding alkylated diethyl-1H-1,2,4-triazol-1-yl-ethyl-1-and-propyl-1-phosphonates 14 and 15 which on hydrolysis with HCI yield 1H-1,2,4-triazol-1-yl-ethyl-1-and propyl-1-phosphonic acids 17 and 18, respectively. Hydrolysis of 4 gives the unsubstituted 1H-1,2,4-triazol-1-ylmethyl-phosphonic acid, 16.     

Chemical constituents from the flowering buds of Bauhinia tomentosa Linn (FBBT)

Isolation and characterisation of compounds, 1-(2′-hydroxy-4′-methoxyphenyl)-3-(4″-methoxyphenyl)-2-hydroxypropane-1,3-dione (1), 5-hydroxyflavone (2), 3,5,7,3′,4′-pentahydroxyflavone (3), 3,5,7,2′,4′-pentahydroxyflavone (4) and 5,7,3′,4′-tetrahydroxyflavone-3-O-rhamnoside (5) are reported from the air dried flowering buds of Bauhinia tomentosa Linn. Their structures are determined on the basis of extensive chemical and spectral evidences. Compound (1) is reported for the first time from the plant source. While compounds (2) and (4) are reported for the first time from this genus, compound (2) is reported for the second time from the natural source.     

AB INITIO MOLECULAR ORBITAL STUDY OF 1,2-DITHIANE AND 1,2,4,5-TETRATHIANE

Ab initio calculations at HF/6-31+G? level of theory for geometry optimization, and MP2/6-31+G?//HF/6-31+G? and B3LYP/6-31+G?//HF/6-31+G? levels for a single-point total energy calculation, are reported for the chair and twist conformations of 1,2-dithiane (1), 3,3,6,6-tetramethyl-1,2-dithiane (2), 1,2,4,5-tetrathiane (3), and 3,3,6,6-tetramethyl-1,2,4,5-tetrathiane (4). The C₂ symmetric chair conformations of 1 and 2 are calculated to be 21.9 and 8.6 kJ mol^?1 more stable than the corresponding twist forms. The calculated energy barriers for chair-to-twist processes in 1 and 2 are 56.3 and 72.8 kJ mol^?1, respectively. The C_2h symmetric chair conformation of 3 is 10.7 kJ mol^?1 more stable than the twist form. Interconversion of these forms takes place via a C₂ symmetric transition state, which is 67.5 kJ mol^?1 less stable than 3-Chair. The D₂ symmetric twist-boat conformation of 4 is calculated to be 4.0 kJ mol^?1 more stable than the C_2h symmetric chair form. The calculated strain energy for twist to chair process is 61.1 kJ mol^?1.     

New and Practical Synthesis of Montelukast Sodium,an Antiasthmatic Drug

Abstract

A new and practical synthesis of montelukast sodium, an antiasthmatic drug, is described. The key steps are the synthesis of nitrile derivative 4 by chiral reduction of keto ester 9 using (?)-DIP-Cl, synthesis of vinylquinoline framework 16 by Wittig reaction, and Heck coupling of nitrile 4 with vinylquinoline 16. The method is operationally simple and suitable for the industrial production of the drug substance.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

HIGHLY DEOXYGENATED SUGARS. I. C2-BRANCHED GLUCOSE DERIVATIVES AND CARBON LINKED DEOXYGENATED DISACCHARIDES *

Triacetylglucal (1) is converted with high α-selectivity (>9:1) to the corresponding 2,3-unsaturated allyl and benzyl glycosides 2 and 3 using ferric chloride as the catalyst. The 6-O-silyl-protected allylic alcohol 5 is transformed to the 3,4-unsaturated C2-branched ester 6 or the amide 7 by Claisen rearrangement. The highly deoxygenated iodo lactone 8, resulting from the amide 6 by iodolactonization, is a versatile starting material for chiral building blocks 9–12. The 3,4-unsaturated C2-branched ester 6 is reduced to the aldehyde 14 and converted to a carbon linked disaccharide analogue 16 via cycloaddition with Danishefky's diene.     

SYNTHESIS OF TWO STABLE DIPHOSPHENES WITH A NEW STABILIZING SUBSTITUENT

Abstract

Two new diphosphenes 7 and 10 have been synthesized by action of DBU on trichlorogermylphosphines 4 and 8; this route involves the intermediate formation of chlorophosphines 5 and 9. Diphosphenes 7 and 10 are stabilized by the 2,6-bis(trifuoromethyl)phenyl group which presents both steric and electronic effects and is used for the first time in phosphorus chemistry.     

Theoretical Studies on S-Phenyl-thiabenzene,S-Phenyl-thianaphthalene,and S-Phenyl-thiaanthracene

The molecular structures of S-phenyl-thiabenzene 1, S-phenyl-1-thianaphthalene 2, S-phenyl-2-thianaphthalene 3, and S-phenyl-9-thiaanthracene 4 are studied by ab initio calculations using HF as well as DFT methods at the 6–311+G? level of theory. The non-planar boat conformers of 1–4 with 6π electrons in the heterocyclic ring appear to be more stable than the corresponding planar conformers with 8π electrons in the ring. The activation energy for the inversion at the sulfur atom is compared for 1–4. Conformational flexibility of 1–4 is studied.     

The crystal and molecular structures of the diastereomeric (4Z)- and (4E)-3-oxo-2,3-dihydrobilatrienes-abc

The molecular and crystal structures of two diastereomeric 3-oxo-2,3-dihydrobilatrienes-abc1 and2 are determined at low (1, 2) and room temperature (2). The configurations at the exocyclic double bond in position 4 are found to be (Z) for1 and (E) for2. Tautomerism, conformation and crystal packing of1 and2 can be understood on the basis of the pattern of intra- and intermolecular hydrogen bonds. Compared to1, a more open helix conformation is found for the (E) diastereomer2. An analysis of crystallographically observed temperature factors of2 yields the result that the highest flexibility is found for the saturated lactam ring.Herrn Prof.Josef Schurz zum 60. Geburtstag gewidmet.     

Heliotropium bacciferum Forssk. (Boraginaceae) extracts: chemical constituents,antioxidant activity and cytotoxic effect in human cancer cell lines

Heliotropium bacciferum (Boraginaceae) is a perennial herb, growing in the Bechar region of Algeria, where it is traditionally used for skin diseases and tonsillitis. Herein, we report the isolation and characterization of sixteen secondary metabolites from the aerial part extracts. They include a sterol (1), megastigman type nor-isoprenoids (2, 3, 4, 6, 8, 10), C-11 terpene lactones (5 and 9), and a monoterpene (7) from the chloroform extract (HB-C); monoterpene glucoside (14), and phenolic compounds (11–13, 15, 16) from the methanol one (HB-M). Their structures were elucidated by spectroscopic methods including 1D and 2D NMR experiments, and ESIMS analysis. HB-M showed a significant and concentration dependent scavenging activity in vitro against the radicals DPPH and ABTS, related to the phenol derivatives (11–13, and 15–16), and HB-C inhibited the growth of colon cancer cell lines, mainly for the presence of the antiproliferative C-11 terpene lactones (5 and 9).     

PHOSPHONIUM YLIDS-VII. SYNTHESIS OF A NEW TYPE OF YLID PHOSPHORANE BY THE ACTION OF WITTIG REAGENTS ON (E)-2-BENZYLIDENEOXAZOLIDINE-4,5-DIONE

Abstract

The reaction of (E)-2-benzylideneoxazolidine-4,5-dione (1) with the methylenetriphenylphosphoranes (2) afforded new ylid-phosphoranes of type 3. The mechanism that accounts for formation of adducts 3 is discussed. Structural reasoning for compounds 3 was based on compatible analytical, chemical and spectroscopic results.     

Synthesis and Solid-State Molecular Structure of Bi(silacyclohexyls) C5H10SiX-XSiC5H10 with X = H,PH, F,CL, BR,and I

The synthesis and purification of novel bi(silacyclohexyls) C₅H₁₀SiX-XSiC₅H₁₀ with X = H (1), Ph (2), F (3), Cl (4), Br (5), and I (6), which are composed of two silacyclohexyl rings connected by a silicon–silicon single bond, is described. Molecular structures for 2, 4, 5, and 6 were determined employing X-ray crystallography. Surprisingly, the SiSi bond lengths increase in the order I < Br < Cl, contrary to what is observed for methylated disilanes Me₂XSiSiXMe₂. The bond lengthening can be traced back to 1, 3 nonbonded interactions between the halogen atoms and the axial hydrogen atoms in the SiC₅ ring, which also cause a decrease of the SiSiX bond angles with increasing size of the halogen atom. Both rings substitute each other in the equatorial position for 4, 5, and 6, but in the axial position for 2.     

Structures,luminescence, and antibacterial studies of two transition metal complexes involving Schiff bases

Two new transition metal complexes of Schiff bases, [Pd₂(L1)₂Cl₂] (1) and [Zn(L2)₂] (2), [L1?=?N-(4-fluorobenzylidene)-2,6-diisopropylbenzenamine and L2?=?2,4-dibromo-6-((E)(mesitylimino)methyl)phenol], have been synthesized solvothermally and characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray diffraction, UV-vis absorption spectra, and single-crystal X-ray diffraction. Complex 1 is a μ-chloro-bridged dinuclear cyclometallated Pd(II) complex, whereas 2 is mononuclear with the Zn^II tetrahedrally coordinated by two L2. Both 1 and 2 display photoluminescence in the solid state at 298?K (fluorescence lifetimes τ?=?22.516?ns at 468?nm for 1, τ?=?3.697?μs at 490?nm for 2). These Schiff bases and their metal compounds have been screened for antibacterial activity against several bacteria, and the results are compared with the activity of penicillin.     

An Improved Asymmetric Synthesis of Unusual Amino Acid (2S,3S)‐3‐Hydroxyproline

Abstract

An improved three‐steps method for the conversion of N‐benzyl (S)‐3‐hydroxypyrrolidin‐2‐one 6 to (2S,3S)‐3‐hydroxyproline 1 is reported. The key step is the reductive cyanation of 6. The synthesis of 1 constitutes a formal asymmetric synthesis of (2S,3S)‐3‐hydroxyproline betaines 2.