2,3-Dihydro-pyrrolo-[2,1-b]quinazoline-9(1H)-thione.

In the crystal, mol-ecules of the title compound, C(11)H(10)N(2)S, are connected by C-H⋯N inter-actions around threefold axes. Furthermore, they form stacks along the c axis showing π-π inter-actions between pyrimidine rings [centroid-centroid distance = 3.721 (1) Å]. The central ring is essentially planar with an r.m.s. deviation of 0.007 Å. The five-membered ring adopts an envelope conformation with the flap atom deviating by 0.241 (4) Šfrom the mean plane (r.m.s. deviation = 0.002 Å) through the other four ring atoms.

Poly[di-µ-chlorido-µ-(1,2,3,9-tetra-hydro-pyrrolo-[2,1-b]quinazolin-9-one-κN:O)-mercury(II)].

In the crystal structure of the title two-dimensional network, [HgCl(2)(C(11)H(10)N(2)O)](n), the asymmetric unit consists of HgCl(2) dumbbells and one mol-ecule of the quinazoline unit. Pseudo-octa-hedrally coordinated Hg(II) cations are chloride-bridged via a crystallographic inversion centre leading to different Hg-Cl bonds (short and long) and linked by other Cl atoms via translation along the a axis. The quinazoline ligands connect the Hg-Cl-Hg-Cl chains by N and O atoms along the b axis, forming the two-dimensional network structure. The crystal structure is stabilized by weak non-classical C-H⋯Cl hydrogen bonds and aromatic π-π stacking inter-actions [centroid-centroid distances = 3.942 (4) and 3.621 (4) Å].

(4-Nitrophenyl)(1,2,3,9-tetrahydro-pyrrolo[2,1-b]quinazolin-3-yl)methanol monohydrate.

In the crystal structure of the title compound, C(18)H(17)N(3)O(3)·H(2)O, the mol-ecules are linked by O-H⋯O and O-H⋯N hydrogen bonds, resulting in a chain along the a axis. The crystal structure is stabilized by weak inter-molecular C-H⋯π (ring) hydrogen bonds and aromatic π⋯π stacking inter-actions [centroid-centroid distance = 3.902 (1) Å] between the pyrimidino rings of the quinazoline system. The tricyclic quinazoline fragment is almost planar (rms deviation = 0.0139 Å) with the two methylene C atoms of the pyrrolo ring deviating by 0.148 (2) and -0.081 (3) Šfrom the plane through the other atoms. The 4-nitrophenyl ring makes a dihedral angle of 12.55 (7)° with the tricyclic ring system.

2-Methyl-4-oxo-6,7,8,9-tetrahydro-thieno[2',3':4,5]pyrimidino-[1,2-a]pyridine-3-carboxylic acid.

There are two independent mol-ecules in the asymmetric unit of the title compound, C(12)H(12)N(2)O(3)S. With the exception of the methyl-ene groups, a mean plane fitted through all non-H atoms of each mol-ecule has an r.m.s. deviation of 0.035 Šfor one mol-ecule and 0.120 Šfor the second. In one of the independent mol-ecules, the methyl-ene groups was refined using a disorder model with an occupancy ratio of 0.53:0.47 (14). Each molecule features an intra-molecular O-H⋯O hydrogen bond, which generates an S(7) ring.

Peptide fragmentation as an approach in modeling of an active peptide and designing a competitive inhibitory peptide for HMG-CoA reductase.

This study presents a simple method to design an active peptide based on a description of the structural preferences of peptide via its peptide fragments. In a previous design, while searching for lead peptide candidates, the efficacy of a design approach that was based on the use of a cyclic peptide as a model of linear analog was demonstrated. Analysis of the conformational behavior of the peptide models showed that an analogical approach could be applied in order to assess the conformational space that was occupied by a peptide by using peptide fragments. In order to assess the proposed method, a design of a competitive inhibitor for HMG-CoA reductase (HMGR) was performed. Two starting points were used in the design: (1) determined recognized residues and (2) the structural preference of a peptide, such as a beta-turn conformation in the present design. Two sets of peptides were developed based on the different location of a beta-turn structure relative to a recognized residue. Set 1 contains peptides in which a recognized residue is included in turn conformation. In Set 2, the turn structure is located distantly from the recognized residues. The design parameter 'V' that was applied in previous studies was slightly modified for the purpose of the current research. The 17 previously and 8 newly designed peptides were estimated by this parameter. In each set, one sequence was selected as a lead peptide candidate for each set: GF(4-fluoro)PEGG for Set 1 and DFGYVAE for Set 2. The inhibitory activities improved in each set. The IC(50) for the GF(4-fluoro)PEGG peptide was found to be 0.75 microM, while the linear DFGYVAE peptide (IC(50)=0.16 microM) showed a 3000-fold increase in inhibitory activity compared to the first isolated LPYP peptide (IC(50)=484 microM) from soybeans. The comparison of the structure-activity relationship (SAR) data between Set 1 and 2 provided an opportunity to design the peptides in terms of peptide selectivity. A structural analysis of the modeled peptides confirmed the appropriateness of the proposed method for the design of active peptides.

9-Furfuryl-idene-2,3-dimethyl-6,7,8,9-tetrahydro-4H--thieno[2',3':4,5]pyrimidino[1,2-a]pyridin-4-one.

The title compound, C(17)H(16)N(2)O(2)S, was obtained by condensation of 2,3-dimethyl-thieno[2',3':4,5]pyrimidino[1,2-a]pyridin-4-one with furfural in the presence of sodium hydroxide. One of the methyl-ene groups of the tetra-hydro-pyrido ring is disordered over two positions in a 0.87 (1):0.13 (1) ratio. The thieno[2,3-d]pyrimidin-4-one unit and the furan ring are both planar (r.m.s. deviation = 0.535 Å), and coplanar with each other, forming a dihedral angle of 5.4 (1)°. Four weak inter-molecular hydrogen bonds (C-H⋯O and C-H⋯N) are observed in the structure, which join mol-ecules into a network parallel to (101).

11-(2-Oxopyrrolidin-1-ylmeth-yl)-1,2,3,4,5,6,11,11a-octa-hydro-pyrido[2,1-b]quinazolin-6-one dihydrate.

In the crystal structure of the title compound, C(17)H(21)N(3)O(2)·2H(2)O, water mol-ecules are mutually O-H⋯O hydrogen bonded and form infinite chains propagating along the b axis. Neighboring chains are linked by the quinazoline mol-ecules by means of O-H⋯O=C hydrogen bonds, forming a two-dimensional network.

(E)-3-[4-(Dimethyl-amino)-benzyl-idene]-2,3-di-hydro-1H,9H-pyrrolo-[2,1-b]quinazolin-9-one.

The title compound, C(20)H(19)N(3)O, was obtained by condensation of 2,3-dihydro-1H,9H-pyrrolo-[2,1-b]quinazolin-9-one (alkaloid de-oxy-vasicinone, isolated from Peganum Harmala) with 4-(dimethyl-amino)-benzaldehyde in the presence of sodium methoxide. The 2,3-dihydro-1H,9H-pyrrolo-[2,1-b]quinazolin-9-one part of the mol-ecule is roughly planar (r.m.s. deviation = 0.0178 Å) and is essentially coplanar with the benzil-idene ring (r.m.s. deviation = 0.0080 Å), forming a dihedral angle of 5.0 (1)°. The crystal structure is stabilized by two aromatic π-π stacking inter-actions observed between the benzene rings of neighboring mol-ecules [centroid-centroid distance = 3.7555 (19) Å.

Synthesis, tautomeric states and crystal structure of (Z)-ethyl 2-cyano-2-(3H-quinazoline-4-ylidene) acetate and (Z)-ethyl 2-cyano-2-(2-methyl-3H-quinazoline-4-ylidene) acetate.

The new compounds (Z)-ethyl 2-cyano-2-(3H- and 2-methyl-3H-quinazoline-4-ylidene) acetate (1 and 2, respectively) were synthesized by multi-step reactions. The structures in a solution have been determined by (1)H-NMR spectroscopy and in the crystal form by X-ray analysis. Molecule 1 crystallized in a primitive monoclinic cell, space group capital ER, P2(1/c). The cell dimensions are a=7.970(6) A, b=7.061(2) A, c=20.537(7) A, beta=97.69(5) degrees , V=1145.3(10) A(3). Molecule 2 crystallized in a triclinic cell, space group P-1, the cell dimensions are a=8.196(5) A, b=8.997(6) A, c=9.435(4) A, alpha=74.22(4) degrees, beta=89.75(4) degrees , gamma=74.07(5) degrees , V=641.9(6) A(3). In both compounds the presence of intra-molecular NH---O=C hydrogen bonding between the nitrogen atom in position 3 of the quinazoline ring and a carbonyl group of the ethyl cyanoacetate residue was proven by quantum-chemical, (1)H-NMR and X-ray methods.