Teo, Yong Chua

Theβ-hydroxyl amino acid unit is a common structural feature of many bioactive marine cyanobacterial depsipeptides. In this study, the absolute stereochemistry of the β-hydroxyl acid moieties in hantupeptins and trungapeptins were determined through their synthesis and HPLC analysis of the Mosher ester derivatives. Synthesis of two3-hydroxy-2-methyloctanoic acid (Hmoa) stereoisomers, (2S,3R)-Hmoa and (2S,3S)-Hmoa, were achieved using diastereoselective asymmetric method and the retention times of all four Hmoa isomers were established indirectly by RPLC-MS analysis of their Mosher ester derivative standards. Based on the retention times of the standards, the absolute configuration of the Hmoa unit in hantupeptin C (3) and trungapeptin C (6) was assigned as (2R,3S)- and (2S,3R)-Hmoa, respectively. The use of the Mosher's reagents, coupled with HPLC analysis, provided a viable alternative to the absolute stereochemical determination of -hydroxy acid units in depsipeptides.

This paper demonstrated a new and economical methodology using Fe(ClO₄)₂·H₂O as a catalyst for the direct C(sp³)–H functionalization of 2-methyl azaarenes via addition to trifluoromethyl ketones. The use of Fe salts as a Lewis acid catalyst has shown great potential as an accessible, affordable, and effective catalyst for the reaction. Under mild, optimized conditions, an extensive range of 2-alkenylated azaarenes was produced with yields of up to 95%.

A practical strategy for the C-N cross-coupling of both aliphatic and aromatic sulfonamides with a variety of substituted aryl bromides is reported. Under the optimized conditions, a good representative of N-arylated products were obtained in good to excellent yields (up to 78 %) under the ligand-free conditions.

A practical and efficient strategy has been developed for the cross-coupling of N,N-dibenzyl-4-iodobenzenesulfonamide with nitrogen nucleophiles using 0.5–20 mol% of CuI under ligand-free conditions. A variety of nitrogen nucleophiles including nitrogen heterocycles, sulfonamides and amides afforded the corresponding products in moderate to good yields (up to 98%) under the optimized conditions. The application of this catalytic system to the synthesis of Celecoxib intermediate was also successfully demonstrated.

An efficient protocol was developed for the N-arylation of 1,2,4-triazoles using substituted aryl bromides catalyzed by CuCl under ligand-free conditions. This method afforded the products in good to excellent yields (up to 88%) under the optimized conditions.

In this paper, we define flip teaching as a curricular platform that uses various strategies, tools, and pedagogies to engage learners in self-directed learning outside the classroom before face-to-face meetings with teachers in the classroom. With this understanding, we adopted flip teaching in the design and enactment of one Year 1 and one Year 2 undergraduate chemistry laboratory session at a higher education institution. The undergraduates viewed videos demonstrating the practical procedures and answered pre-laboratory questions posted on the institution's mobile device application before the laboratory lessons. Analyses of the lesson videos, interviews with the undergraduates and instructors, and undergraduate artefacts showed that the undergraduates had developed a better understanding of the theory undergirding the procedures before they performed the practical, and were able to decipher the complex practical procedures. They also experienced less anxiety about the complex practical steps and setup, and subsequently, improved work efficiency. The findings of this study have implications for chemistry educators looking for ways to improve on the design and enactment of the laboratory curriculum to enhance the undergraduates' self-directed learning.