Pyrrole-ligated 1,3,4-oxadiazole is a very important pharmacophore which exhibits broad therapeutic effects such as anti-tuberculosis, anti-epileptic, anti-HIV, anti-cancer, anti-inflammatory, antioxidant, and antibacterial activities. A one-pot Maillard reaction between D-Ribose and an L-amino methyl ester in DMSO with oxalic acid at 2.5 atm and 80 °C expeditiously produced pyrrole-2-carbaldehyde platform chemicals in reasonable yields, which were utilized for the synthesis of pyrrole-ligated 1,3,4-oxadiazoles. Benzohydrazide reacted with the formyl group of the pyrrole platforms to provide the corresponding imine intermediates, which underwent I2-mediated oxidative cyclization to the pyrrole-ligated 1,3,4-oxadiazole skeleton. The structure and activity relationship (SAR) of the target compounds with varying alkyl or aryl substituents of the amino acids and electron-withdrawing or electron-donating substituents on the phenyl ring of benzohydrazide were evaluated for antibacterial activity against Escherichia coli, Staphylococcus aureus, and Acinetobacter baumannii as representative Gram(–) and Gram(+) bacteria. Branched alkyl groups from the amino acid showed better antibacterial activities. Absolutely superior activities were observed for 5f-1 with an iodophenol substituent against A. baumannii (MIC < 2 μg/mL), a bacterial pathogen that displays a high resistance to commonly used antibiotics.

2,7-Diphenalkyl-4-octenedials 3 were prepared for the syntheses of 13,13 0diphenalkyl β-carotenes 1b-1d, which serve as the intramolecular models for the π-stacking interactions of chlorophylls and carotenoids. The optimal tether length of the 13-phenalkyl substituents in carotenes 1b-1d for the maximum π-π interactions with the polyene chain was decided to be a three-methylene unit based on the most up-field chemical shifts of the nearby protons of H 11 and H 15 by the magnetic anisotropic effect of benzene rings, which would provide a valuable information in the assembly of a single molecular light-harvesting/energy-transferring unit for artificial photosynthetic system. K E Y W O R D S carotenoids, chemical shift, energy transfer, photosynthesis, pi interactions Boram Lim and Young-Hun Kim contributed equally to this study.

Practical synthetic methods of biogenetically and pharmaceutically important phytofluene were developed through divergent preparation of key C20 substrates from a common intermediate and convergent synthesis by Wittig and Julia-Kocienski olefinations. Expeditious synthesis of phytofluene was also proposed based on the Julia sulfone-mediated chain-extension and double elimination method. Stereochemical outcomes of these olefination methods for phytofluene were compared and the Julia-Kocienski method was the mildest and most efficient reaction condition to produce all-(E)-phytofluene. Complete 1H- and 13C-NMR analysis of all-(E)-phytofluene was reported for the first time. Phytofluene underwent facile thermal isomerization to other Z-isomers above room temperature, which was also confirmed by the C30 phytofluene homologue.