Indolizine 1-sulfonates as potent inhibitors of 15-lipoxygenase from soybeans

Ethyl 3-benzoyl-indolizine-1-carboxyl-ate

The title compound, C₁₈H₁₅NO₃, consists of an indolizine ring system and an aromatic ring. The two ring systems are not coplanar, the dihedral angle between the two being 54.26 (7)°. In the crystal, inversion dimers are formed by weak C—H⋯O interactions. These dimeric groups are further extended to form a regular two-dimensional structure by additional weak C—H⋯O inter­actions.

(8aRS)-8,8a-Dihydro-furo[3,2-f]indolizine-6,9(4H,7H)-dione

The title compound, C(10)H(9)NO(3), is a chiral mol-ecule with one stereogenic carbon atom, but which crystallizes as a racemate in the centrosymmetric space group P2(1)/n. The central six-membered ring of the indolizine moiety adopts a definite envelope conformation, while the conformation of the oxopyrrolidine ring is close to that of a flat-envelope with a maximum deviation of 0.352 (1) Å for the flap atom.

Amberlite-IRA-402 (OH) ion exchange resin mediated synthesis of indolizines, pyrrolo [1,2-a] quinolines and isoquinolines: antibacterial and antifungal evaluation of the products

A number of indolizines and pyrrolo[1,2-a]quinolines/isoquinolines were prepared from phenacyl pyridinium, quinolinium and isoquinolinium salts derived from the reaction of the heterocycles with 2-bromo acetophenone with alkynes and alkenes using amberlite-IRA-402 (OH) ion exchange resin as the base. Antibacterial and antifungal studies were carried out against thirteen bacterial and four fungal strains, which revealed that three derivatives (4a, 4b, 7a) out of fifteen are effective against all the thirteen strains and one derivative, 10, showed dual antibactericidal and antifungal efficacy.

Diethyl indolizine-1,3-dicarboxyl-ate

The title compound, C(14)H(15)NO(4), was prepared by a 1,3-dipolar cyclo-addition from N-(eth-oxy-carbonyl-methy)pyridinium bromide and ethyl acrylate. The -CO(2) side chains form dihedral angles of 0.2 (3) and 2.4 (3)° with respect to the ring system. In the crystal, two neighbouring mol-ecules form a dimer through weak C-H⋯O interactions. The dimers form a three-dimensional structure via further weak C-H⋯O inter-actions.

Methyl 9-(4-bromo-phen-yl)-8a,9,9a,10,11,12,13,14a-octa-hydro-8H-benzo[f]chromeno[3,4-b]indolizine-8a-car-box-ylate

In the title compound, C₂₇H₂₆BrNO₃, the mean plane of the naphthalene ring system makes a dihedral angle of 22.0 (1)° with the bromo-substituted benzene ring. The pyrrolidine and piperidine rings exhibit envelope and chair conformations, respectively. An inter­molecular C—H⋯Br inter­action is observed.

Effects of detergents on the West Nile virus protease activity

Detergents such as Triton X-100 are often used in drug discovery research to weed out small molecule promiscuous and non-specific inhibitors which act by aggregation in solution and undesirable precipitation in aqueous assay buffers. We evaluated the effects of commonly used detergents, Triton X-100, Tween-20, Nonidet-40 (NP-40), Brij-35, and CHAPS, on the enzymatic activity of West Nile virus (WNV) protease. Unexpectedly, Triton X-100, Tween-20, and NP-40 showed an enhancement of in vitro WNV protease activity from 2 to 2.5-fold depending on the detergent and its concentration. On the other hand, Brij-35, at 0.001% enhanced the protease activity by 1.5-fold and CHAPS had the least enhancing effect. The kinetic analysis showed that the increase in protease activity by Triton X-100 was dose-dependent. Furthermore, at Triton X-100 and Tween-20 concentrations higher than 0.001%, the inhibition of compound B, one of the lead compounds against WNV protease identified in a high throughput screen (IC(50) value of 5.7+/-2.5 microM), was reversed. However, in the presence of CHAPS, compound B still showed good inhibition of WNV protease. Our results, taken together, indicate that nonionic detergents, Triton X-100, Tween, and NP-40 are unsuitable for the purpose of discrimination of true versus promiscuous inhibitors of WNV protease in high throughput assays.

(7R,8R,8aS)-8-Hydr-oxy-7-phenyl-per-hydro-indolizin-3-one

The absolute configuration of the title compound, C(14)H(17)NO(2), was assigned from the synthesis. There are two mol-ecules in the asymmetric unit. Their geometries are very similar and corresponding bond lengths are almost identical [mean deviation for all non-H atoms = 0.015 (2) Å]. The six-membered ring of the indolizine system adopts a chair conformation. In the crystal structure, mol-ecules form chains parallel to the a axis via inter-molecular O-H⋯O hydrogen bonds, which help to stabilize the crystal structure.

Multisubstituted N-fused heterocycles via transition metal-catalyzed cycloisomerization protocols

Two complementary protocols for assembly of multisubstituted N-fused heterocycles have been developed. It was demonstrated that 1,3-disubstituted N-fused heterocycles, including indolizines, pyrroloquinoxalines, and pyrrolothiazoles can easily be synthesized via an exceptionally mild and efficient method involving a novel silver-catalyzed cycloizomerization of propargyl-containing heterocycles. Alternatively, 1,2-disubstituted heterocycles can be accessed through the novel cascade transformation involving an alkyne-vinylidene isomerization with concomitant 1,2-shift of hydrogen, silyl, stannyl, or germyl groups. This mild and simple method allows for selective and highly efficient synthesis of indolizines, pyrroloisoquinolines, pyrroloquinoxalines, pyrrolopyrazines, and pyrrolothiazoles.

(11R,11aS)-11-Hydr-oxy-1,5,11,11a-tetra-hydro-1-benzothieno[2,3-f]indolizin-3(2H)-one

The absolute configuration of the title compound, C₁₄H₁₃NO₂S, was assigned from the synthesis and confirmed by the structure determination. The central six-membered ring of the indolizine system adopts an envelope conformation, the greatest deviation from the mean plane of the ring being 0.459 (2) Å for the N atom. The benzothieno system is planar [mean deviation = 0.009 (2) Å]. In the crystal structure, mol­ecules form chains parallel to the b axis via inter­molecular O—H⋯O hydrogen bonds.

Synthesis of indolizine derivatives with selective antibacterial activity against Mycobacterium tuberculosis

1-substituted indolizines with activity against Mycobacterium tuberculosis have been synthesized. The most active compounds carry an hydroxyphenylmethyl- or hydroxyalkyl substituent in the indolizine 1-position. The alkyl chain should be moderately long (C-5 or C-6). Aryl groups in the 2- and 3-position of the indolizine are also required. Removal of the 3-substituent resulted in significant loss of activity. A nitrile substituent in the 7-position is beneficial for both chemical stability and bioactivity. The compounds studied display a narrow antibacterial spectrum and appear to be quite selective antimycobacterial compounds. Moderate activity against certain pathogenic protozoa was also observed.

Promiscuous Ligands

Computational and experimental high-throughput screening are frequently used to discover new leads for drug design. Although novel ligands have been identified by these methods, it has become clear that screening hit lists are plagued by false positives. These nuisance compounds are ultimately found to be developmental dead-ends and are abandoned, often after considerable effort has been invested in them. Much work over the last decade has been devoted to exploring the origins of false-positive screening hits, and ligand promiscuity has emerged as one such cause. Well-known mechanisms of promiscuity include reactive species and privileged substructures. More recently, it has been found that some nonspecific screening hits form aggregates of 30–1000 nm in diameter. It has been proposed that these aggregate particles are responsible for the promiscuous behavior of many false positives and that aggregate-forming compounds may be widespread among screening hits. This chapter will review the known mechanisms of ligand promiscuity with an emphasis on the recently described model of aggregation. Experimental and computational methods for identifying promiscuous compounds will be described, and some outstanding questions in the field will be considered.