Gel growth of α and γ glycine and their characterization

The microbial free single crystals of α and γ glycine were grown from gel at room temperature in a new chemical route. These crystals showed a superior quality than the solution grown crystals. The metastable α-form and the stable γ-form of glycine were crystallized in silica gel by solubility reduction method. The form of crystallization is confirmed by single crystal and powder X-ray diffraction analyses. The crystals of α and γ glycine were found to crystallize in monoclinic and hexagonal crystal systems, respectively. For analyzing the functional group and thermal stability of α and γ glycine crystals, spectroscopic and thermal analyses have been carried out. The dielectric studies were performed to find the dielectric constant of the grown crystals and the results are discussed. Second harmonic generation efficiency of the crystal was measured by Kurtz’s powder method using Nd:YAG laser and it was found to be 2.68 times that of potassium dihydrogen phosphate crystals.     

Stereoselective construction of quaternary chiral centers using Ti(III)-mediated opening of 2,3-epoxy alcohols: studies directed toward the synthesis of penifulvins

A trisubstituted α,β-unsaturated ester moiety was suitably placed in a molecule also bearing an epoxy alcohol moiety at its other end to intramolecularly trap the intermediate radical, which was formed when the molecule was treated with Cp₂Ti(III)Cl to regio- and stereoselectively open its epoxy ring, giving rise to a quaternary chiral center. The method was subsequently used in an attempt to construct the bicyclic core framework of potent insecticides penifulvins.     

Influence of Helium-Neon Laser Irradiation on Seed Germination In Vitro and Physico-Biochemical Characters in Seedlings of Brinjal (Solanum melongena L.) var. Mattu Gulla

In the present study, the seeds of brinjal (Solanum melongena L.) var. Mattu Gulla were irradiated with single exposure of He–Ne laser at different doses of 5–40 J cm^?2 and germinated aseptically. Thirty day old seedlings were harvested and the germination, growth, physiological and biochemical parameters were estimated and compared with un‐irradiated control seedlings. A significant enhancement in growth characters were noted with respect to length, fresh and dry weight of shoots and roots. In addition, chlorophyll (a and b), carotenoid content, anthocyanin and amylases (α and β) activities were found to be altered. Significant alterations in percentage of seed germination (P < 0.001) and time to 50% germination (P < 0.001) were observed in the irradiated seeds compared with the un‐irradiated controls. In conclusion, the results of the present study demonstrated that low dose (5–30 J cm^?2) of He–Ne laser irradiation enhanced the germination process and altered growth, by positively influencing physiological and biochemical parameters of the brinjal seedlings compared with un‐irradiated control under in vitro conditions.     

Concise synthesis of chiral pyrazolo[4,3-f] [1,4]oxazepines and pyrazolo[4,3-f] [1,4]thiazepines bearing pyrazole unit

An efficient synthesis of pyrazolo [1,4]-oxazepines and [1,4]-thiazepines bearing a variety of alkyl and aryl groups with a chiral center has been developed. The synthesis started with readily available 5-chloro-pyrazole-4-carbaldehyde and chiral amino alcohols. The key step involves intramolecular imine formation. These classes of compounds are potentially useful as templates for drug discovery.     

Effect of Heme–Heme Interactions and Modulation of Metal Spins by Counter Anions in a Series of Diiron(III)‐μ‐hydroxo Bisporphyrins: Unusual Stabilization of Two Different Spins in a Single Molecular Framework

A new family of five ethene‐bridged diiron(III)‐μ‐hydroxo bisporphyrins with the same core structure but different counter anions, represented by the general formula [Fe₂(bisporphyrin)]OH ? X (X=counter anion), is reported herein. In these complexes, two different spin states of Fe are stabilized in a single molecular framework. Protonation of the oxo‐bridged dimer 1 by strong Brønsted acids such as HI, HBF₄, HPF₆, HSbF₆, and HClO₄ produces the μ‐hydroxo complexes with I₅^? ( 2 ), BF₄^? ( 3 ), PF₆^? ( 4 ), SbF₆^? ( 5 ), and ClO₄^? ( 6 ) as counter anions, respectively. The X‐ray structures of 2 and 6 have been determined, which provide a rare opportunity to investigate structural changes upon protonation. Spectroscopic characterization has revealed that the two iron(III) centers in 2 are nonequivalent with nearly high and admixed‐intermediate spins in both the solid state and solution. Moreover, the two different Fe^III centers of 3 – 5 are best described as having admixed‐high and admixed‐intermediate spins with variable contributions of S=5/2 and 3/2 for each state in the solid, but two different admixed‐intermediate spins in solution. In contrast, the two Fe^III centers in 6 are equivalent and are assigned as having high and intermediate spin states in the solid and solution, respectively. The X‐ray structures reveal that the Fe? O bond length increases on going from the μ‐oxo to the μ‐hydroxo complexes, and the Fe‐O(H)‐Fe unit becomes more bent, with the dihedral angle decreasing from 150.9(2)° in 1 to 142.3(3)° and 143.85(2)° in 2 and 6 , respectively. Variable‐temperature magnetic data have been subjected to a least‐squares fitting using the expressions derived from the spin Hamiltonians H=?2JS₁?S₂?μ?B+D[${S{{2\hfill \atop z\hfill}}}$ ?1/3S(S+1)] (for 2 , 3 , 4 , and 5 ) and H=?2JS₁?S₂ (for 6 ). The results show that strong antiferromagnetic coupling between the two Fe^III centers in 1 is attenuated to nearly zero (?2.4 cm^?1) in 2 , whereas the values are ?46, ?32.6, ?33.5, and ?34 cm^?1 for 3 , 4 , 5 , and 6 , respectively.     

Synthesis and antimicrobialactivity of 2‐alkylcarbamato‐2,3‐dihydro‐5‐propylthio‐1H‐1,3,2‐benzodiazaphosphole 2‐oxides

Novel 2‐alkylcarbamato/thiocarbama‐to‐2,3‐dihydro‐5‐propylthio‐1H‐1,3,2‐benzodiazaphos‐phole 2‐oxides ( 4a–J ) were synthesized by cyclization of 4‐propylthio‐1,2‐phenylenediamine ( 3 ) with the corresponding dichlorophosphoryl carbamates/thiocarbamates ( 2a–J ) that were obtained by the addition of alcohols/thiols to isocyanatophosphoryl dichloride ( 1 ). The structures of the title compounds were confirmed by the ¹H, ¹³C, ³¹P NMR, and mass spectral studies. Some of these products were found to possess significant antimicrobial activity. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:336–340, 2000