An Efficient Approach to Chiral C8/C9-Piperazino-Substituted 1,4-Benzodiazepin-2-ones as Peptidomimetic Scaffolds

Synthesis and biological evaluation of novel 1,4-benzodiazepin-3-one derivatives as potential antitumor agents against prostate cancer

A novel tumor suppressing agent was discovered against PC-3 prostate cancer cells from the screening of a 1,4-benzodiazepin-3-one library. In this study, 96 highly diversified 2,4,5-trisubstituted 1,4-benzodiazepin-3-one derivatives were prepared by a two-step approach using sequential Ugi multicomponent reaction and simultaneous deprotection and cyclization to afford pure compounds bearing a wide variety of substituents. The most promising compound showed a potent and selective antiproliferative activity against prostate cancer cell line PC-3 (GI₅₀ = 10.2 µM), but had no effect on LNCAP, LAPC4 and DU145 cell lines. The compound was initially prepared as a mixture of two diastereomers and after their separation by HPLC, similar antiproliferative activities against PC-3 cells were observed for both diastereomers (2S,5S: GI₅₀ = 10.8 µM and 2S,5R: GI₅₀ = 7.0 µM). Additionally, both diastereomers showed comparable stability profiles after incubation with human liver microsomes. Finally, in vivo evaluation of the hit compound with the chick chorioallantoic membrane xenograft assay revealed a good toxicity profile and significant antitumor activity after intravenous injection.

The status of isocyanide-based multi-component reactions in Iran (2010-2018)

Isocyanides as key intermediates and magic reactants have been widely applied in organic reactions for direct access to a broad spectrum of remarkable organic compounds. Although the history of these magical compounds dates back more than 100 years, it still has been drawing widespread attention of chemists who confirmed their versatility and effectiveness. Because of their wide spectrum of pharmacological, industrial and synthetic applications, many reactions with the utilization of isocyanides are reported in the literature. In this context, Iranian scientist played a significant role in the growth of isocyanides chemistry. The present review article covers literature from the period starting from 2010 onward and encompasses new synthetic routes and organic transformation involving isocyanides by Iranian researchers. During this period, a diverse range of isocyanide-based multi-component reactions (I-MCRs) has been reported such as a new modification of Ugi, post-Ugi, Passerini and Groebke-Blackburn-Bienayme condensation reactions, isocyanide-based [1 + 4] cycloaddition reactions, isocyanide-acetylene-based MCRs, isocyanide and Meldrum's acid-based MCRs, several unexpected reactions besides green mediums and novel catalytic systems for the synthesis of diverse kinds of pharmaceutically and industrially remarkable heterocyclic and linear organic compounds. This review also emphasizes the neoteric applications of I-MCR for the synthesis of valuable peptide and pseudopeptide scaffolds, enzyme immobilization and functionalization of materials with tailorable properties that can play important roles in the plethora of applications.

Continuous flow synthesis of diaryl ketones by coupling of aryl Grignard reagents with acyl chlorides under mild conditions in the ecofriendly solvent 2-methyltetrahydrofuran

An efficient continuous flow sequential synthesis of diaryl ketones was achieved by coupling of aryl Grignard reagents with acyl chlorides in the bio-derived “green” solvent 2-methyltetrahydrofuran (2-MeTHF) under mild reaction conditions (ambient temperature, 1 hour), allowing a safe and on-demand generation of 2-(3-benzoylphenyl)propionitrile with a productivity of 3.16 g hour⁻¹.

Continuous flow method for parallel synthesis of diaryl ketones using commercially available reagents.

Synthesis of 2-aminobenzophenones through acylation of anilines with α-oxocarboxylic acids assisted by tert-butyl nitrite

A highly facile all-in-one-pot synthesis of 2-aminobenzophenones directly from anilines, tert-butyl nitrite and α-oxocarboxylic acids under the catalysis of Pd(OAc)₂ is presented.

Application of the Ugi reaction with multiple amino acid-derived components: synthesis and conformational evaluation of piperazine-based minimalist peptidomimetics

The concurrent employment of α-amino acid-derived chiral components such as aldehydes and α-isocyanoacetates, in a sequential Ugi reaction/cyclization two-step strategy, opens the door to the synthesis of three structurally distinct piperazine-based scaffolds, characterized by the presence of L-Ala and/or L-Phe-derived side chains and bearing appropriate functionalities to be easily applied in peptide chemistry. By means of computational studies, these scaffolds have been demonstrated to act as minimalist peptidomimetics, able to mimic a well defined range of peptide secondary structures and therefore potentially useful for the synthesis of small-molecule PPI modulators. Preliminary biological evaluation of two different resistant hepatocellular carcinoma cellular lines, for which differentiation versus resistance ability seem to be strongly correlated with well defined types of PPIs, has revealed a promising antiproliferative activity for selected compounds.

The structural evolution of β-secretase inhibitors: a focus on the development of small-molecule inhibitors

Effective treatment of Alzheimer's disease (AD) remains a critical unmet need in medicine. The lack of useful treatment for AD led to an intense search for novel therapies based on the amyloid hypothesis, which states that amyloid β-42 (Aβ42) plays an early and crucial role in all cases of AD. β-Secretase (also known as BACE-1 β-site APP-cleaving enzyme, Asp-2 or memapsin-2) is an aspartyl protease representing the rate limiting step in the generation of Aβ peptide fragments, therefore it could represent an important target in the steady hunt for a disease-modifying treatment. Generally, β-secretase inhibitors are grouped into two families: peptidomimetic and nonpeptidomimetic inhibitors. However, irrespective of the class, serious challenges with respect to blood-brain barrier (BBB) penetration and selectivity still remain. Discovering a small molecule inhibitor of β-secretase represents an unnerving challenge but, due to its significant potential as a therapeutic target, growing efforts in this task are evident from both academic and industrial laboratories. In this frame, the rising availability of crystal structures of β-secretase-inhibitor complexes represents an invaluable opportunity for optimization. Nevertheless, beyond the inhibitory activity, the major issue of the current research approaches is about problems associated with BBB penetration and pharmacokinetic properties. This review follows the structural evolution of the early β-secretase inhibitors and gives a snap-shot of the hottest chemical templates in the literature of the last five years, showing research progress in this field.

Novel peptidomimetics as BACE-1 inhibitors: synthesis, molecular modeling, and biological studies

Aiming at identifying new scaffolds for BACE-1 inhibition devoid of the pharmacokinetic drawbacks of peptide-like structures, we investigated a series of novel peptidomimetics based on a 1,4-benzodiazepine (BDZ) core 1a-h and their seco-analogues 2a-d. We herein discuss synthesis, molecular modeling and in vitro studies which, starting from 1a, led to the seco-analogues (R)-2c and (S)-2d endowed with BACE-1 inhibition properties in the micromolar range both on the isolated enzyme and in cellular studies. These data can encourage to pursue these analogues as hits for the development of a new series of BACE-1 inhibitors active on whole-cells.

Synthesis of benzodiazepine beta-turn mimetics by an Ugi 4CC/Staudinger/aza-Wittig sequence. Solving the conformational behavior of the Ugi 4CC adducts

5-Oxobenzo[e][1,4]diazepine-3-carboxamides were synthesized by sequential Ugi reaction-Staudinger/aza-Wittig cyclization. The pseudopeptidic backbone of the new benzodiazepine derivatives superimposed well with type I, I', II, and II' beta-turn motifs. The intermediate Ugi adducts were characterized as two conformers of the enol form by the correlation between (1)H NMR spectra and X-ray diffraction structures of model compounds.

Complete mapping of the stereochemical course of retentive deprotonation/alkylation of 1H-benzo[e][1,4]diazepin-2(3H)-ones

Enantiopure amino-acid derived 1H-benzo[e][1,4]diazepin-2(3H)-ones (BZDs) undergo highly retentive deprotonation/alkylation reactions. To confirm the role of stereolabile, axially chiral intermediates in these reactions and to determine the precise stereochemical course of deprotonation and alkylation, a new alanine-derived BZD (S)-1d was prepared. Because of slow diazepine ring inversion of the C3-alkylated derivatives of 1d, it proved possible to determine that electrophiles react at the concave face of the enolate derived from 1d. Furthermore, an enantiopure silyl enol ether derivative of (S)-1d was prepared and characterized by X-ray crystallography, confirming that deprotonation resulted in an (M)-configured axially chiral enolate. Activation parameters for diazepine ring inversion in the potassium enolate of 1d were determined experimentally and are well-matched by density functional calculations. Finally, the factors leading to concave-face alkylation of the enolate derived from 1d are analyzed based on calculated alkylation transition structures. Minimization of torsional effects at the BZD ring fusion and maximization of imine and amide resonance are proposed to favor concave-face alkylation.