Asymmetric Catalysis: Resin-Bound Hydroxyprolylthreonine Derivatives in Enamine-Mediated Reactions

Green Asymmetric Organocatalysis

Asymmetric organocatalysis is becoming one of the main tools for the synthesis of chiral compounds that are needed as medicines, crop protection agents, and other bioactive molecules. It can be effectively combined with various green chemistry methodologies. Intensification techniques, such as ball milling, flow, high pressure, or light, bring not only higher yields, faster reactions, and easier product isolation, but also new reactivities. More sustainable reaction media, such as ionic liquids, deep eutectic solvents, green solvent alternatives, and water, also considerably enhance the sustainability profile of many organocatalytic reactions.

Final-stage site-selective acylation for the total syntheses of multifidosides A-C

The first total syntheses of multifidosides A-C have been achieved. The synthetic strategy is characterized by catalytic site-selective acylation of unprotected glycoside precursors in the final stage of the synthesis. High functional-group tolerance of the site-selective acylation, promoted by an organocatalyst, enabled the conventionally difficult molecular transformation in a predictable and reliable manner. An advantage of this strategy is to avoid the risks of undesired side reactions during the removal of the protecting groups at the final stage of the total synthesis.

Halogenated benzimidazole carboxamides target integrin alpha4beta1 on T-cell and B-cell lymphomas

Integrin alpha(4)beta(1) is an attractive but poorly understood target for selective diagnosis and treatment of T-cell and B-cell lymphomas. This report focuses on the rapid microwave preparation, structure-activity relationships, and biological evaluation of medicinally pertinent benzimidazole heterocycles as integrin alpha(4)beta(1) antagonists. We documented tumor uptake of derivatives labeled with (125)I in xenograft murine models of B-cell lymphoma. Molecular homology models of integrin alpha(4)beta(1) predicted that docked halobenzimidazole carboxamides have the halogen atom in a suitable orientation for halogen-hydrogen bonding. The high-affinity halogenated ligands identified offer attractive tools for medicinal and biological use, including fluoro and iodo derivatives with potential radiodiagnostic ((18)F) or radiotherapeutic ((131)I) applications, or chloro and bromo analogues that could provide structural insights into integrin-ligand interactions through photoaffinity, cross-linking/mass spectroscopy, and X-ray crystallographic studies.