Enguang Feng

The 2009 pandemic H1N1 neuraminidase N1 lacks the 150-cavity in its active site

Influenza A virus neuraminidase can be classified into groups 1 and 2 on the basis of its primary structure. The main structural feature of group 1 neuraminidase is an extra cavity in the active site, the 150-cavity. Here we present the crystal structure of neuraminidase from the 2009 pandemic H1N1 influenza strain. In contrast to other characterized N1 neuraminidases, which are all members of group 1, 2009 H1N1 neuraminidase does not have a 150-cavity.

Structural and functional analysis of laninamivir and its octanoate prodrug reveals group specific mechanisms for influenza NA inhibition

The 2009 H1N1 influenza pandemic (pH1N1) led to record sales of neuraminidase (NA) inhibitors, which has contributed significantly to the recent increase in oseltamivir-resistant viruses. Therefore, development and careful evaluation of novel NA inhibitors is of great interest. Recently, a highly potent NA inhibitor, laninamivir, has been approved for use in Japan. Laninamivir is effective using a single inhaled dose via its octanoate prodrug (CS-8958) and has been demonstrated to be effective against oseltamivir-resistant NA in vitro. However, effectiveness of laninamivir octanoate prodrug against oseltamivir-resistant influenza infection in adults has not been demonstrated. NA is classified into 2 groups based upon phylogenetic analysis and it is becoming clear that each group has some distinct structural features. Recently, we found that pH1N1 N1 NA (p09N1) is an atypical group 1 NA with some group 2-like features in its active site (lack of a 150-cavity). Furthermore, it has been reported that certain oseltamivir-resistant substitutions in the NA active site are group 1 specific. In order to comprehensively evaluate the effectiveness of laninamivir, we utilized recombinant N5 (typical group 1), p09N1 (atypical group 1) and N2 from the 1957 pandemic H2N2 (p57N2) (typical group 2) to carry out in vitro inhibition assays. We found that laninamivir and its octanoate prodrug display group specific preferences to different influenza NAs and provide the structural basis of their specific action based upon their novel complex crystal structures. Our results indicate that laninamivir and zanamivir are more effective against group 1 NA with a 150-cavity than group 2 NA with no 150-cavity. Furthermore, we have found that the laninamivir octanoate prodrug has a unique binding mode in p09N1 that is different from that of group 2 p57N2, but with some similarities to NA-oseltamivir binding, which provides additional insight into group specific differences of oseltamivir binding and resistance.

Gold-catalyzed one-pot cascade construction of highly functionalized pyrrolo[1,2-a]quinolin-1(2H)-ones.

An efficient protocol was developed for the synthesis of fused heterocyclic multiring compounds pyrrolo[1,2-a]quinolin-1(2H)-ones via a AuBr(3)/AgSbF(6)-catalyzed cascade transformation. Significantly, the strategy affords a straightforward and efficient approach to construction of tricyclic lactam molecular architectures in which two new C-C bonds and one new C-N bond are formed in a one-pot synthetic operation from simple starting materials. Moreover, a broad spectrum of substrates can participate in the process effectively to produce the desired products in good yields and with excellent regio- and chemoselectivities.

Regioselective Synthesis of 3-Benzazepinones and Unexpected 5-Bromo-3-benzazepinones

A regioselective hydroamidation of 2-(1-alkynyl)phenylacetamides with Au(PPh(3))Cl/AgSbF(6) as the catalyst proceeded by a 7-endo-dig pathway to afford 3-benzazepinones. This method accommodates a broad range of alkyl and aryl alkynyl substitutes in moderate to high yields (63-91%). Moreover, unexpectedly, we also discovered a gold-mediated transformation from 2-(1-alkynyl)phenylacetamides to 5-bromo-3-benzazepinones, and AuBr(3) was found to not only play an activation role but also act as a reactant in the reaction for the first time.

Gold-catalyzed intramolecular hydroamination of terminal alkynes in aqueous media: efficient and regioselective synthesis of indole-1-carboxamides

Using [Au(PPh3)]Cl/Ag2CO3-catalyzed 5-endo-digcyclization in water under microwave irradiation, we developed a fast and green route to prepare indole-1-carboxamides from N′-substituted N-(2-alkynylphenyl)ureas. The described method is tolerant to a variety of functional groups, including N′-aryl, alkyl, heterocyclic, various N-(substituted-2-ethynylphenyl) and N-(2-ethynylpyridin-3-yl)ureas and affords moderate to high yields of the desired products.

Recent Advances in Neuraminidase Inhibitor Development as Anti-influenza Drugs

The recent emergence of the highly pathogenic H5N1 subtype of avian influenza virus (AIV) and of the new type of human influenza A (H1N1) have emphasized the need for the development of effective anti‐influenza drugs. Presently, neuraminidase (NA) inhibitors are widely used in the treatment and prophylaxis of human influenza virus infection, and tremendous efforts have been made to develop more potent NA inhibitors to combat resistance and new influenza viruses. In this review, we discuss the structural characteristics of NA catalytic domains and the recent developments of new NA inhibitors using structure‐based drug design strategies. These drugs include analogues of zanamivir, analogues of oseltamivir, analogues of peramivir, and analogues of aromatic carboxylic acid and present promising options for therapeutics or leads for further development of NA inhibitors that may be useful in the event of a future influenza pandemic.

Gold(I)-Catalyzed Tandem Transformation: A Simple Approach for the Synthesis of Pyrrolo/Pyrido[2,1-a][1,3]benzoxazinones and Pyrrolo/Pyrido[2,1-a]quinazolinones

We have developed a simple method for the synthesis of pyrrolo/pyrido[2,1-a][1,3]benzoxazinones and pyrrolo/pyrido[2,1-a]quinazolinones from 2-amino benzoic acids and 2-amino benzamides via a gold(I)-catalyzed tandem coupling/cyclization process. The tricyclic or polycyclic molecular architectures were constructed in one pot with the formation of three new bonds.

Copper(I)-catalyzed one-pot synthesis of 2H-1,4-benzoxazin-3-(4H)-ones from o-halophenols and 2-chloroacetamides.

We developed an efficient and convenient method for preparing N-substituted 2H-1,4-benzoxazin-3-(4H)-ones from 2-halophenols via a nucleophilic substitution with 2-chloroacetamides followed by a CuI-catalyzed coupling cyclization. A broad spectrum of substrates can be effectively employed to afford the desired products in good yields. Since this method involves simple reaction conditions, a short reaction time, and a broad substrate scope, it is particularly attractive for the efficient preparation of biologically and medicinally interesting molecules.

Gold-catalyzed tandem reaction in water: an efficient and convenient synthesis of fused polycyclic indoles

This report describes the gold-catalyzed synthesis of fused polycyclic indoles from substituted 2-(1H-indol-1-yl) alkylamines and alkynoic acids in water under microwave irradiation. This protocol proceeds in high atom economy and leads to the generation of two rings, together with the formation of one new C–C bond and two new C–N bonds in a single operation. The advantages of the method include a short reaction time, excellent yield, easy work-up, and the use of microwave irradiation and an environmentally benign solvent.

Design and synthesis of small molecule RhoA inhibitors: a new promising therapy for cardiovascular diseases?

RhoA is a member of Rho GTPases, a subgroup of the Ras superfamily of small GTP-binding proteins. RhoA, as an important regulator of diverse cellular signaling pathways, plays significant roles in cytoskeletal organization, transcription, and cell-cycle progression. The RhoA/ROCK inhibitors have emerged as a new promising treatment for cardiovascular diseases. However, to date, RhoA inhibitors are macromolecules, and to our knowledge, small molecular-based inhibitors have not been reported. In this study, a series of first-in-class small molecular RhoA inhibitors have been discovered by using structure-based virtual screening in conjunction with chemical synthesis and bioassay. Virtual screening of ∼200,000 compounds, followed by SPR-based binding affinity assays resulted in three compounds with binding affinities to RhoA at the micromolar level (compounds 1-3). Compound 1 was selected for further structure modifications in considering binding activity and synthesis ease. Fourty-one new compounds (1, 12a-v, 13a-h, and 14a-j) were designed and synthesized accordingly. It was found that eight (12a, 12j, 14a, 14b, 14d, 14e, 14 g, and 14h) showed high RhoA inhibition activities with IC(50) values of 1.24 to 3.00 μM. A pharmacological assay indicated that two compounds (14g and 14 h) demonstrated noticeable vasorelaxation effects against PE-induced contraction in thoracic aorta artery rings and served as good leads for developing more potent cardiovascular agents.