Rules of Chemospecificity of Nucleophilc Ring-opening of Dithia-/Oxathia-Phospholane Towards the Selective Synthesis of Nucleoside 5’-O-Pα-Thio/Dithio/Trithio-Phosphate Ester Conjugates

DBU-assisted nucleophilic ring-opening of both uridine-5’-(2-thio-1,3,2-dithia-phospholane), 3, and uridine-(2-thio-1,3,2-oxathia-phospholane), 8, lasted 2 min at RT and resulted in quantitative yields of uridine-5’-phosphoro-di/trithioate esters. Furthermore, it was selective for alcohol and thiol vs. amine nucleophiles. Yet, reaction of mercaptoethanol with 3, was chemo-specific for the oxygen vs. sulfur nucleophile, while for the reaction of mercaptoethanol with 8, the opposite chemo-specificity was observed, probably related to the steric hindrance in the former case. The observed chemospecificity opens facile avenue for the synthesis of nucleoside-5’-O-Pα-thio/dithio/trithio-phosphate ester derivatives

Microwave Heating Promotes the S-Alkylation of Aziridine Catalyzed by Molecular Sieves: A Post-Synthetic Approach to Lanthionine-Containing Peptides

Aziridine derivatives involved in nucleophilic ring-opening reactions have attracted great interest, since they allow the preparation of biologically active molecules. A chemoselective and mild procedure to convert a peptide cysteine residue into lanthionine via S-alkylation on aziridine substrates is presented in this paper. The procedure relies on a post-synthetic protocol promoted by molecular sieves to prepare lanthionine-containing peptides and is assisted by microwave irradiation. In addition, it represents a valuable alternative to the stepwise approach, in which the lanthionine precursor is incorporated into peptides as a building block.

(1R,4S,5S)-5-((3-Hydroxypropyl)amino)-4-((1-Methyl-1H-tetrazol-5-yl)thio)Cyclopent-2-en-1-ol

Using environmentally friendly conditions, the nucleophilic ring-opening reaction of 6-azabicyclo[3.1.0]hex-3-en-2-ol with 1-methyl-1H-tetrazole-5-thiol provided a novel thiol-incorporated aminocyclopentitol, (1R,4S,5S)-5-((3-hydroxypropyl)amino)-4-((1-methyl-1H-tetrazol-5-yl)thio)cyclopent-2-en-1-ol, in excellent yield (95%). The newly synthesized compound was analyzed and characterized via 1H, 13C-NMR, HSQC, and mass spectral data.

Role of Click Chemistry in Organic Synthesis

Click chemistry involves highly efficient organic reactions of two or more highly functionalized chemical entities under eco-benign conditions for the synthesis of different heterocycles. Several organic reactions such as nucleophilic ring-opening reactions, cyclo-additions, nucleophilic addition reactions, thiol-ene reactions, Diels Alder reactions, etc. are included in click reactions. These reactions have very important features i.e. high functional group tolerance, formation of a single product, high atom economy, high yielding, no need for column purification, etc. It also possesses several applications in drug discovery, supramolecular chemistry, material science, nanotechnology, etc. Being highly significant and valuable, we have elaborated on several aspects of click reactions in organic synthesis in this chapter. Recent advancements in the field of organic synthesis using click chemistry approach have been deliberated by citing last five years articles.

Electrically conductive and light-weight branched polylactic acid-based carbon nanotube foams

In spite of the high electrical conductivity of carbon nanotube (CNT), its tendency to aggregate and expensive cost in fabricating aerogel, foams, and porous materials remains a problem. Therefore, we described a simple and feasible way to design light-weight, high electrically conductive, and cost-efficient polylactic acid (PLA)/CNT foams. The branched PLA (BPLA) resin with excellent melt elasticity and foamability was induced by nucleophilic ring-opening reaction of epoxy-based acrylic/styrene copolymer and PLA. After that, BPLA/CNT composites and foams were prepared by melt-mixing and supercritical carbon dioxide foaming technology, respectively. The thermal, electrical, and foaming properties were studied. The resultant BPLA/CNT foam possessed a low density of 0.174 g/cm3 and high crystallinity of 3.03%. An improvement of the oriented structure of CNT induced by cell growth in BPLA matrix increased the conductivity of the foam up to 3.51 × 104 Ω/m. The proposed foaming materials provided a way for designing and preparing high performance CNT products.