Multicomponent Approach to a Library of N-Substituted γ-Lactams

Ugi 5-center-4-component reaction of α-amino aldehydes and its application in synthesis of 2-oxopiperazines

A synthetic route leading to densely functionalized 2-oxopiperazines is presented. The strategy employs a 5-center-4-component variant of Ugi multicomponent reaction followed by a deprotection/cyclization sequence. N-Boc-α-amino aldehydes were used for the first time as carbonyl components in a key Ugi 5-center-4-component reaction (U-5C-4CR). It is shown that the presented synthetic route can lead to rigid, heterocyclic scaffolds, as demonstrated by the synthesis of tetrahydro-2H-pyrazino[1,2-a]pyrazine-3,6,9(4H)-trione β-turn mimetic and derivatives of 1,6-dioxooctahydropyrrolo[1,2-a]pyrazine and 3,8-dioxohexahydro-3H-oxazolo[3,4-a]pyrazine.

The Ugi three-component reaction and its variants

A broad variety of α-aminoamide-based compounds have been synthesized via the three-component version of the Ugi reaction (U-3CR) or by any of its variants (Ugi-Zhu-3CR, Orru-3CR, Ugi-4C-3CR, Ugi-Joullié-3CR, GBB-3CR, Ugi-Reissert-3CR, and so on).

Optimization and utilization of single chain metallocatanionic vesicles for antibacterial photodynamic therapy (aPDT) against E. coli

Currently, bacterial infection due to multi-drug-resistant bacteria is one of the foremost problems in public health. Photodynamic therapy plays a significant role against bacterial infection, without causing any side effects. But the photosensitizers are associated with many drawbacks, which lessen their photodynamic efficiency. In this context, the current study describes the synthesis of new metallocatanionic vesicles and employs them in photodynamic therapy. These vesicles were synthesized by using a single-chain cationic metallosurfactant (CuCPC I) and sodium oleate (NaOl) as an anionic component. These vesicles were characterized from conductivity, dynamic light scattering, zeta potential, field emission scanning electron microscopy, and confocal microscopy measurements. Methylene blue (MB) was used as a photosensitizer and its singlet oxygen quantum yield in the presence of these vesicles was determined by irradiating with 650 nm wavelength laser light. These vesicles play a dual-functional role, one helping in delivering the photosensitizer and the second doubling their singlet oxygen production capability due to the presence of metal ions. Antibacterial photodynamic therapy (aPDT) was studied against E. coli bacteria (Gram-negative bacteria). These vesicles also inherit their antibacterial activity and MB-encapsulated metallocatanionic vesicles on irradiation have shown 100% killing efficiency. In summary, we offer metallocatanionic vesicles prepared via a facile approach, which encapsulate a photosensitizer and can be used to combat E. coli infection through photodynamic therapy. We envisage that these synthesized metallocatanionic vesicles will provide a new modification to the catanionic mixture family and could be used for various applications in the future.

One-pot five-component high diastereoselective synthesis of polysubstituted 2-piperidinones from aromatic aldehydes, nitriles, dialkyl malonates and ammonium acetate

A novel five-component diastereoselective synthesis of polysubstituted 2-piperidinones is reported. The Knoevenagel condensation-Michael addition-Mannich cascade of two equivalents of aromatic aldehydes, nitriles, dialkyl malonates and ammonium acetate or aqueous ammonia in alcohols provides convenient access to alkyl (3SR,4RS,6SR)-5,5-dicyano-2-oxo-4,6-diarylpiperidine-3-carboxylates with three stereocenters in 52-90% or dialkyl (2SR,3RS,4RS,5SR)-2,4-diaryl-3-cyano-6-oxopiperidine-3,5-dicarboxylates with four stereocenters in 38-88%. The formation of products was highly stereoselective, with only one diastereomer formed. Ammonium acetate or aqueous ammonia plays a role both as a catalyst and as a nitrogen source. 2,4,6-triaryl-3,3,5,5-tetracyanopiperidines were obtained as a side products in the reactions with nitro-substituted aldehydes or with ethyl and n-propyl cyanoacetates. A series of 14 2-piperidinones and piperidines was assessed for antimicrobial activity against a panel of five bacteria and two fungi; no significant activity was observed. Two side piperidines with nitro substituents in aromatic ring possess bacteriostatic action against S. aureus ATCC 43300 and A. baumannii ATCC 19606 at 32 ug/mL.

Ruthenium-catalyzed synthesis of N-substituted lactams by acceptorless dehydrogenative coupling of diols with primary amines

Herein, we report the first example of synthesis of N-substituted lactams via an acceptorless dehydrogenative coupling of diols with primary amines in one step, which was enabled by combining Ru3(CO)12 with a hybrid N-heterocyclic carbene-phosphine-phosphine ligand as the catalyst.