Sanjay Sarkhel

A Convenient Synthesis and Hepatoprotective Activity of Imidazo(1,2-c)pyrimido(5,4-e)pyrimidine, Tetraazaacenaphthene and Tetraazaphenalene from Cyclic Ketene Aminals Through Tandem Addition-Cyclization Reactions {

A novel one-pot synthesis of imidazo[1,2-c]pyrimido[5,4-e]pyrimidinones (2), tetraazaacenaphthene-3,6-diones (4), tetarazaphenalene-1,7-dione (4d) is delineated from the reaction of cyclic ketene aminal (1) and alkyl or aryl isothiocyanate through tandem addition-cyclization reactions. However, reaction of ketene aminal (1a) with alkyl isothiocyanate only yielded angularly cyclized product 5 which did not react further to yield 6. The structure of 2c and 4d was ascertained by single crystal X-ray diffraction analysis which demonstrated a network of various inter- and intramolecular interactions, responsible for the stability and packing of the molecules in the crystalline state. Some of the compounds (2a--h) were screened for hepatoprotective activity but only 2a was found most effective.

1H NMR and X-ray crystallographic analysis of 1,2-bis(4,6-diethylthio-1H-pyrazolo[3,4-d]pyrimidin-1-yl)ethane and its ‘propylene linker’-analog: molecular recognition versus crystal engineering ☆

Abstract Proton NMR analysis on newly synthesized 1,2-bis(4,6-diethylthio-1H-pyrazolo[3,4-d]pyrimidin-1-yl)ethane, 2c , and 1,2-bis(4,6-diethylthio-1H-pyrazolo[3,4-d]pyrimidin-1-yl)propane, 2d , showed intramolecular stacking in solution. X-Ray crystallography on 2c and 2d , however, confirmed the presence of such intramolecular stacking only in case of the ‘propylene linker’ compound, 2d , while the ‘ethylene linker’ compound, 2c , was devoid of it.

Resolution, molecular structure and biological activities of the D- and L-enantiomers of potent anti-implantation agent, DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran.

Compound 1 (DL-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran, CDRI 85/287) a potent anti-estrogen and anti-implantation agent has been successfully resolved into its pure D- and L-enantiomers. Biological studies showed L-enantiomer to be the active form, exhibiting a fivefold higher receptor affinity for the rat uterine cytosolic estrogen receptor, 100% contraceptive efficacy at 1.3 mg/kg dose in single day schedule and 89% inhibition of estradiol induced increase of uterine weight at its contraceptive dose. The absolute stereochemistry determined by X-ray crystallographic analysis showed that the L-enantiomer has 2R configuration at its asymmetric centre.

Disappearance of intramolecular stacking due to one-atom movement or increment of a `propyl­ene linker' in pyrazolo­[3,4-d]­pyrimidine-based ­flexible models

In the crystal structures of 4,6-dimethylthio-1-[3-(4, 6-dimethylthio-2H-pyrazolo[3, 4-d]pyrimidin-2-yl)propyl]-1H-pyrazolo[3,4-d]pyrimidine, C(17)H(20)N(8)S(4), and 1-[4-(4-methoxy-6-methylthio-1H-pyrazolo[3, 4-d]pyrimidin-1-yl)butyl]-5-methyl-6-methylthio-4, 5-dihydro-1H-pyrazolo[3,4-d]pyrimidin-4-one, C(18)H(22)N(8)O(2)S(2), only intermolecular stacking due to aromatic pi-pi interactions between pyrazolo[3,4-d]pyrimidinerings is present.

A dimeric layered structure of a 4-oxo-4,5-di­hydro-1H-pyrazolo­[3,4-d]­pyrimidine compound

The title compound, 6-methylsulfanyl-1-(3-phenylpropyl)-4,5-dihydro-1H-pyrazolo[3,4-d]pyrimidin-4-one, C(15)H(16)N(4)OS, crystallizes in space group Pbca, with two molecules of similar structure in the asymmetric unit. The molecular structure shows the absence of intramolecular stacking in the crystalline state, as indicated by earlier (1)H NMR analysis in solution. In addition, the crystal packing reveals the formation of a layered structure, due mainly to intermolecular N[bond]H...O[double bond]C hydrogen bonding and arene-arene interactions.

A facile access to the synthesis of functionalised unsymmetrical biaryls from 2H-pyran-2-ones through carbanion induced C–C bond formation

A convenient synthesis of highly functionalised biaryls 3 and 6 has been delineated through carbanion induced C–C bond formation from 6-aryl-3-cyano-4-substituted-2H-pyran-2-ones (1, 4) and acetone. Extension of this reaction, using aromatic ketones led to (4,6-diarylpyran-2-ylidene)acetonitrile (7) in lieu of the anticipated 2,4-diaryl-6-methylthiobenzonitrile (8). The structure of 2-methyl-6-methylthio-4-(3,4-methylenedioxyphenyl)benzonitrile (3f) was ascertained by single crystal X-ray diffraction analysis and displayed a variety of weak interactions, responsible for the stability and packing of the molecule in the crystalline state.

Dysobinin, a tetranortriterpenoid

The planar furan ring in the title compound (6beta-acetoxyazadirone, C(30)H(38)O(6)) is twisted with respect to the steroid D ring. The crystal structure is stabilized by C-H.O hydrogen bonds and van der Waals interactions.

7-methoxy-2,2-dimethyl-3-phenyl-4-(4-hydroxyphenyl)-2H-1-benzopyran

The crystal structure of the title compound, C 24 H 22 O 3 , shows that both the pendant phenyl substituents at C3 and C4 have a twist conformation, while the pyran ring adopts a distorted sofa conformation due to puckering at C2 by the dimethyl substitutions.

A highly functionalized ferrocenylpyrazolo[2,3-a]pyridine.

The crystal structure of [2-(4-bromophenyl)-4-cyano-5-ferrocenylpyrazolo[2,3-a]pyridin-7-yl]acetonitrile, C(26)H(17)N(4)FeBr or [Fe(C(5)H(5))(C(21)H(12)BrN(4))], shows that the pyrazolopyridine ring system (PP), the bromophenyl ring (BP) and the cyclopentadiene ring (Cp) are nearly planar. The PP ring system is twisted out of the plane of the BP and Cp rings by about 20 degrees.