Highlights

•Multimers of the proline-rich antimicrobial peptide, ChexArg20, were prepared

•Increase in peptide valency alters its Escherichia coli membrane interaction

•Change is from membrane non-lytic to membrane disruption

•There is also simultaneous change from membrane hyperpolarization to depolarization

A series of N- and C-terminal modifications of the monomeric proline-rich antimicrobial peptide, Chex1-Arg20, was obtained via different chemical strategies using Fmoc/tBu solid-phase peptide synthesis in order to study their effects on a panel of Gram-negative bacteria. In particular, C-terminal modifications with hydrazide or alcohol functions extended their antibacterial activity from E. coli and K. pneumoniae to other Gram-negative species, A. baumannii and P. aeruginosa. Furthermore, these analogues did not show cytotoxicity towards mammalian cells. Hence, such modifications may aid in the development of more potent proline-rich antimicrobial peptides with a greater spectrum of activity against Gram-negative bacteria than the parent peptide.

The increasing resistance of pathogens to antibiotics causes a huge clinical burden that places great demands on academic researchers and the pharmaceutical industry for resolution. Antimicrobial peptides, part of native host defense, have emerged as novel potential antibiotic alternatives.

In one-pot cascade reaction, a series of functionalized 3-aroyl-4-hydroxy-4-arylpiperidine derivatives were prepared from sulfonamides and vinyl ketones with good to excellent yields and diastereoselectivities. The reaction was catalyzed by the commercially available Lewis base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and could be easily manipulated under mild condition.

We present a highly efficient strategy for obtaining a series of chiral 2,4-disubstituted thiazolone derivatives with excellent diastereo- and enantioselectivities through the creation of carbon- and nitrogen-substituted quaternary carbon stereocenters. With the chiral tertiary amine-thiourea catalyst developed by our group, the reactions could be performed smoothly at 1 mol-% catalyst loadings without any additive. Preliminary biological evaluation demonstrated that these analogues could inhibit cell proliferation in vitro significantly.

A highly efficient catalyst system assembled from enantiomerically pure diaminocyclohexane and Ni(OAc)2 is, for the first time, used to catalyze the cascade Michael–Henry reaction of various diones and substituted nitroalkenes.

The highly enantioselective Michael addition of malonates to α,β-unsaturated ketones in water was reported to be catalyzed by a primary−secondary diamine catalyst containing a long alkyl chain. This asymmetric Michael addition process was found to be effective for a variety of α,β-unsaturated ketones.