Design and synthesis of 6-amino-1,4-oxazepane-3,5-dione derivatives as novel broad spectrum anticonvulsants

Transposition of an acrylate moiety in TMSOTf-mediated reaction of alkynyl vinylogous carbonates gives heterocyclic dienes

TMSOTf-mediated reaction of alkynyl vinylogous carbonates serendipitously gave 1,4-oxazepine and dihydropyran dienes via transposition of an ethyl acrylate moiety involving intramolecular cascade Prins-type cyclization/retro-oxa-Michael reaction/cycloisomerisation. The developed atom-economical protocol selectively provides an E double bond geometry. Dihydropyran dienes could be reduced diastereoselectively using Et₃SiH/TMSOTf or could be transformed into polycyclic heterocycles by Heck reaction.

Conceptual design and cost-efficient environmentally Benign synthesis of beta-lactams

Stereoselective preparation of diverse trans and cis β-lactams following different experimental conditions are executed. A variety of circumstances are critically analyzed. It has been found that the stereochemistry of the products depends on a number of parameters including the conditions of the procedures, composition of the Schiff bases and acid chlorides or equivalents, method of addition of the reactants, temperature of the process and nature of the media. Using some of the compounds and methods as described herein, a number of useful chemical transformations for the preparation of heterocycles are achieved. These methods include indium-catalyzed glycosylation of amino β-lactams, preparation of pyrrole-substituted β-lactams, cycloaddition with sterically congested Schiff bases towards β-lactams, Michael reaction for the preparation of polycyclic oxazepenes and synthesis of two chiral isomers of the thienamycin side chain. Most of the products are obtained stereospecifically and in optically active forms. Many reactions described here are catalytic and therefore, these are environmentally friendly.

Discovery of glyantrypine-family alkaloids as novel antiviral and antiphytopathogenic-fungus agents

BACKGROUND

Plant diseases caused by viruses and fungi have caused great losses to crop quality and yield. The discovery of novel and efficient antiviral and antiphytopathogenic-fungus agents is urgently needed. It is the most important pesticide innovation strategy to find active compounds from natural products. Here, glyantrypine-family alkaloids were taken as the parent structures and a series of their derivatives were designed through molecular splicing, ring expansion, and ring contraction strategies, and synthesized. The anti-tobacco mosaic virus (TMV) activities and antifungal activities of these alkaloids were systematically investigated for the first time.

RESULT

The antiviral activities of compounds 7bb, 7bc, 11c, 18b, 18d, 28d, and 28e are equivalent to or better than that of ribavirin (inhibitory rates 39%, 37%, and 40% at 500 μg mL^-1 for inactivation, curative, and protection activity in vivo, respectively). Compounds 18d and 28d with good antiviral activities were selected for antiviral mode of action studies, which indicated that these alkaloids could achieve good antiviral effects by inhibiting TMV particle extension during assembly. These compounds also exhibited broad-spectrum fungicidal activities.

CONCLUSION

Glyantrypine-family alkaloids and their derivatives were synthesized and evaluated for anti-TMV and fungicidal activities for the first time. Compounds 18d and 28d with excellent antiviral activities and compound 7bc with remarkable fungicidal activity emerged as novel lead compounds. This study lays a foundation for the application of glyantrypine alkaloids in plant protection.

Atomic and molecular properties of nonclassical bioisosteric replacements of the carboxylic acid group

Aim: Drug design is fraught with challenges as small differences in the structure of a drug molecule can significantly affect its biological activity. Bioisosteres are interchangeably used to adjust pharmacokinetic and pharmacodynamic properties without affecting the biological activity of the drug. While electrostatic potential maps (EPMs) are typically used to show the similarity in the 'key and lock' interactions between a drug and its receptor, they are limited to qualitative comparisons. Methodology & results: Using the quantum theory of atoms in molecules, quantitative similarities among nonclassical bioisosteres of carboxylic acid were evaluated. Conclusion: The similarity in the bioisosteric groups was captured with the average electron density tool which generated remarkably close average electron densities regardless of the capping group, the isodensity values or the protonation state of the molecule. The similarities among bioisosteres was less obvious using the EPM tool.

Expeditious diastereoselective synthesis of medium ring heterocycle-fused chromenes via tandem 8/9-endo-dig and 8-exo-dig hydroalkoxylation-formal-[4 + 2] cycloaddition

The first examples of highly diastereoselective tandem 8/9-endo-dig and 8-exo-dig hydroalkoxylation-formal-[4 + 2] cycloaddition are described for the synthesis of medium ring heterocycle-fused chromenes. TMS-alkynols preferred the exo-dig mode of hydroalkoxylation over the endo-dig mode leading to spiro-cyclic chromenes. The method could be used for the synthesis of linearly-fused ladder-like polyethers. A thia-heterocycle-fused chromene could be transformed into a complex bridged tricyclic ketal by a tandem carbene-insertion-[2,3]-sigmatropic shift.

An efficient synthesis of 16H-dibenzo[2,3:6,7][1,4]oxazepino[5,4-b]quinazolin-16-ones via an Ullmann reaction catalyzed by CuI

CuI functions as a mild Lewis acid catalyst to promote the condensation and cyclization reaction of 2-amino-N-(2-hydroxyphenyl)benzamide and 2-bromobenzaldehyde to build the quinazoline moiety first. With the addition of Cs₂CO₃, it also can catalyse the subsequent intramolecular Ullmann type reaction to give 16H-dibenzo[2,3:6,7][1,4]oxazepino[5,4-b]quinazolin-16-ones in good yields.

New route to 1,4-oxazepane and 1,4-diazepane derivatives: synthesis from N-propargylamines

N-Propargylamines are one of the most useful and versatile building blocks in organic synthesis that are successfully transformed into many significant N-heterocycles.

7-endo selenocyclization reactions on chiral 3-prenyl and 3-cinnamyl-2-hydroxymethylperhydro-1,3-benzoxazine derivatives. A way to enantiopure 1,4-oxazepanes

Enantiopure 1,4-oxazepane derivatives have been prepared by selenocyclofunctionalization of chiral 3-prenyl- and 3-cinnamyl-2-hydroxymethyl-substituted perhydro-1,3-benzoxazine derivatives. The 7-endo-cyclization occurs in high yields and diastereoselection. The regio- and stereochemistry of the cyclization products was dependent on the substitution pattern of the double bond, the nature of the hydroxyl group and the experimental conditions.

Amino acid chirons: a tool for asymmetric synthesis of heterocycles

As a result of their easy availability in enantiomerically enriched form and their possession of synthetically transformable diverse functional groups, amino acids have been extensively used by synthetic organic and medicinal chemists as a chiral pool for access to heterocycles (monocycles, bicycles or polycycles, either bridged or fused). This review describes the syntheses of diverse asymmetric heterocycles with various membered rings (n = 3-9) followed by benzo or heteroannulated ones, for the period from 1996 to Dec. 2013. It details solution phase synthetic methodologies in which the naturally occurring α-amino acid is incorporated, totally or partially, into the final product.

Design, synthesis, anticonvulsant and analgesic studies of new pyrazole analogues: a Knoevenagel reaction approach

Compounds1a,4aand7a(76.58, 79.76 and 78 94% protection) shows potent anticonvulsant activity compounds1b,5a,5b,7aand7bshowed good analgesic property.

Copper catalysed [3 + 2] cycloaddition with concomitant annulation: formation of 2,4-diaryl-1,4-oxazepan-7-ones via a ketenimine route

A novel strategy of copper catalyzed cascade reaction involving intramolecular nucleophilic addition to N-sulfonylketenimine gratifyingly furnishing 1,4-diaryl oxazepan-7-one has been described.

Primary amino acid derivatives: substitution of the 4'-N'-benzylamide site in (R)-N'-benzyl 2-amino-3-methylbutanamide, (R)-N'-benzyl 2-amino-3,3-dimethylbutanamide, and (R)-N'-benzyl 2-amino-3-methoxypropionamide provides potent anticonvulsants with pain-attenuating properties

Recently, we reported that select N'-benzyl 2-substituted 2-amino acetamides (primary amino acid derivatives (PAADs)) exhibited pronounced activities in established whole animal anticonvulsant (i.e., maximal electroshock seizure (MES)) and neuropathic pain (i.e., formalin) models. The anticonvulsant activities of C(2)-hydrocarbon N'-benzyl 2-amino acetamides (MES ED(50) = 13-21 mg/kg) exceeded those of phenobarbital (ED(50) = 22 mg/kg). Two additional studies defining the structure-activity relationship of PAADs are presented in this issue of the journal. In this study, we demonstrated that the anticonvulsant activities of (R)-N'-benzyl 2-amino-3-methylbutanamide and (R)-N'-benzyl 2-amino-3,3-dimethylbutanamide were sensitive to substituents at the 4'-N'-benzylamide site; electron-withdrawing groups retained activity, electron-donating groups led to a loss of activity, and incorporating either a 3-fluorobenzyloxy or 3-fluorophenoxymethyl group using a rationally designed multiple ligand approach improved activity. Additionally, we showed that substituents at the 4'-N'-benzylamide site of (R)-N'-benzyl 2-amino-3-methoxypropionamide also improved anticonvulsant activity, with the 3-fluorophenoxymethyl group providing the largest (∼4-fold) increase in activity (ED(50) = 8.9 mg/kg), a value that surpassed phenytoin (ED(50) = 9.5 mg/kg). Collectively, the pharmacological findings provided new information that C(2)-hydrocarbon PAADs represent a novel class of anticonvulsants.