Crystal structure of 2,2′-(p-tolylazanediyl)bis(1-phenylethan-1-one), C23H21NO2

C23H21NO2, monoclinic, C2/c (no. 15), a = 20.163(3) Å, b = 10.1693(16) Å, c = 8.8032(19) Å, β = 95.992(12)°, V = 1795.2(4) Å3, Z = 4, R gt (F) = 0.0624, wR ref(F 2) = 0.1411, T = 150 K.

Structurally simple synthetic 1, 4-disubstituted piperidines with high selectivity for resistant Plasmodium falciparum

Background

Emergence of resistance to artemisinins and some of their combinations in chemotherapy of clinical malaria has intensified the search for novel safe efficacious antimalarial molecules. Fourteen synthetic 1, 4-disubstituted piperidines with simple molecular structures were evaluated in this study.

Methods

Antiplasmodial activity were determined against cultured chloroquine-sensitive 3D7 and resistant Dd2 strains of P. falciparum by in vitro parasite growth inhibition. A primary screen was done to identify active compounds by fluorescence microscopy followed by a secondary screen to determine IC₅₀ and IC₉₀ values of active compounds by the parasite lactate dehydrogenase assay. Cytotoxicity of active compounds was assessed using the MTT/formazan assay and selectivity indices (SIs) determined. Optical densities were analysed to obtain experimental results.

Results

The compounds produced 56 to 93% inhibition of parasite growth at 40 μg/mL. Eight compounds (2 ketone, 5 alcohol and one amine analogues) showed high activity (IC₅₀s between 1 and 5 μg/mL). Nine compounds were highly selective for the parasite (SIs = 15 to 182). Three promising (alcohol) analogues were identified: [1-(4-fluorobenzyl) piperidin-4-yl] [4-fluorophenyl] methanol, (7), [1-(3, 4-dichlorobenzyl) piperidin-4-yl] [4- fluorophenyl] methanol (8) and [1-(4-bromobenzyl) piperidin-4-yl] [4- fluorophenyl] methanol (11) which were more active on the resistant strain (IC₅₀ values between 1.03 to 2.52 μg/mL), than the sensitive strain (IC₅₀ values between 2.51 to 4.43 μg/mL).

Conclusions

The alcohol analogues were the most active and most selective for the parasite with three promising hit molecules identified among them, suggesting the hydroxyl group at C-7’ in these alcohol analogues is contributing greatly to their antiplasmodial activity. Further exploration of the core structure using chemistry approaches and biological screening including in vivo studies in an animal model of malaria may yield important antimalarial leads.

Microwave-Assisted Synthesis of Bioactive Six-Membered Heterocycles and Their Fused Analogues

This review describes the formation of six-membered heterocyclic compounds and their fused analogues under microwave activation using modern organic transformations including cyclocondensation, cycloaddition, multicomponents and other modular reactions. The review is divided according to the main heterocycle types in order of increasing complexity, starting with heterocyclic systems containing one, two and three heteroatoms and their fused analogues. Recent microwave applications are reviewed, with special focus on the chemistry of bioactive compounds. Selected examples from the 2006 to 2015 literature are discussed.

Three closely-related cyclohexanols (C35H27X2N3O3; X = F, Cl or Br): similar molecular structures but different crystal structures

Three highly-substituted cyclohexanol derivatives have been prepared from 2-acetylpyridine and 4-halogenobenzaldehydes under mild conditions. (1RS,2SR,3SR,4RS,5RS)-3,5-Bis(4-fluorophenyl)-2,4-bis(pyridine-2-carbonyl)-1-(pyridin-2-yl)cyclohexanol, C35H27F2N3O3, (I), (1RS,2SR,3SR,4RS,5RS)-3,5-bis(4-chlorophenyl)-2,4-bis(pyridine-2-carbonyl)-1-(pyridin-2-yl)cyclohexanol acetone 0.951-solvate, C35H27Cl2N3O3·0.951C3H6O, (II), and (1RS,2SR,3SR,4RS,5RS)-3,5-bis(4-bromophenyl)-2,4-bis(pyridine-2-carbonyl)-1-(pyridin-2-yl)cyclohexanol, C35H27Br2N3O3, (III), all crystallize in different space groups, viz. Pbca, Fdd2 and P1, respectively. In compound (II), the acetone molecule is disordered over two sets of atomic sites having occupancies of 0.690 (13) and 0.261 (13). Each of the cyclohexanol molecules contains an intramolecular O-H···N hydrogen bond and their overall molecular conformations are fairly similar. The molecules of (I) are linked by two independent C-H···O hydrogen bonds to form a C(5)C(10)[R2(2)(15)] chain of rings, and those of (III) are linked by a combination of C-H···O and C-H···N hydrogen bonds, forming a chain of alternating R2(2)(16) and R2(2)(18) rings. The cyclohexanol molecules in (II) are linked by a single C-H···N hydrogen bond to form simple C(4) chains and these chains are linked by a π-π stacking interaction to form sheets, to which the disordered acetone molecules are weakly linked via a number of C-H···O contacts.

Ultrasound-mediated synthesis of N,N-bis(phenacyl)aniline under solvent-free conditions

Abstract

An efficient method for the synthesis of N,N-bis(phenacyl)anilines was developed via smooth condensation of anilines with α-bromoacetophenones in the presence of sodium carbonate as acid acceptor and polyethylene glycol 400 (PEG 400) as catalyst at room temperature under solvent-free conditions by using 350 W ultrasound irradiation. In addition to experimental simplicity, the main advantages of the procedure are mild conditions, short reaction times (30–45 min), and high yields (73–83 %).

Graphical Abstract

Organometallic enantiomeric scaffolding: a strategy for the enantiocontrolled construction of regio- and stereodivergent trisubstituted piperidines from a common precursor

Reported herein is a general and efficient method to construct 2,3,6-trisubstituted piperidines in a substituent-independent fashion. From the high enantiopurity organometallic scaffold (-)-Tp(CO)(2)[(η-2,3,4)-(1S,2S)-1-benzyloxycarbonyl-5-oxo-5,6-dihydro-2H-pyridin-2-yl)molybdenum (Tp = hydridotrispyrazolylborato), a variety of TpMo(CO)(2)-based 2,3,6-trifunctionalized complexes of the (η-3,4,5-dihydropyridinyl) ligand were easily obtained in 5 steps through a sequence of highly regio- and stereospecific metal-influenced transformations (15 examples). From the 2,3,6-trifunctionalized molybdenum complexes, either 2,6-cis-3-trans or 2,3,6-cis systems were selectively obtained through the choice of an appropriate stereodivergent demetalation protocol. The potential of this strategy in synthetic chemistry was demonstrated by the short total synthesis of four natural and one non-natural alkaloids: indolizidines (±)-209I and (±)-8-epi-219F in the racemic series, and enantiocontrolled syntheses of (-)-indolizidine 251N, (-)-quinolizidine 251AA, and (-)-dehydroindolizidine 233E.