Diastereodivergent Synthesis of 4-Hydroxy-2,3-methanopipecolic Acid Derivatives as Conformationally Constrained Homoserine Analogues

Asymmetric Reduction of Cyclic Imines by Imine Reductase Enzymes in Non-Conventional Solvents

The first enantioselective reduction of 2-substituted cyclic imines to the corresponding amines (pyrrolidines, piperidines, and azepines) by imine reductases (IREDs) in non-conventional solvents is reported. The best results were obtained in a glycerol/phosphate buffer 1 : 1 mixture, in which heterocyclic amines were produced with full conversions (>99 %), moderate to good yields (22-84 %) and excellent S-enantioselectivities (up to >99 % ee). Remarkably, the process can be performed at a 100 mM substrate loading, which, for the model compound, means a concentration of 14.5 g L-1 . A fed-batch protocol was also developed for a convenient scale-up transformation, and one millimole of substrate 1 a was readily converted into 120 mg of enantiopure amine (S)-2 a with a remarkable 80 % overall yield. This aspect strongly contributes to making the process potentially attractive for large-scale applications in terms of economic and environmental sustainability for a good number of substrates used to produce enantiopure cyclic amines of high pharmaceutical interest.

Recent advances in the synthesis of analogues of phytohormones strigolactones with ring-closing metathesis as a key step

In this paper, we synthesized and evaluated the biological activity of structural analogues of natural strigolactones in which the butenolide D-ring has been replaced with a γ-lactam. The key step to obtain the α,β-unsaturated-γ-lactam was an RCM on suitably substituted amides. Strigolactones (SLs) are plant hormones with various developmental functions. As soil signaling chemicals, they are required for establishing beneficial mycorrhizal plant/fungus symbiosis. Beside these auxinic roles, recently SLs have been successfully investigated as antitumoral agents. Peculiar to the SL perception system is the enzymatic activity of the hormone receptor. SARs data have shown that the presence of the butenolide D-ring is crucial to retain the biological activity. The substitution of the butenolide with a lactam might shed light on the mechanism of perception. In the following, a dedicated in silico study suggested the binding modes of the synthesized compounds to the receptor of SLs in plants.

Stereodivergent synthesis of 5-aminopipecolic acids and application in the preparation of a cyclic RGD peptidomimetic as a nanomolar αVβ3 integrin ligand

A stereodivergent preparation of trans and cis-5-aminopipecolic acids (5-APAs) was developed to obtain constrained amino acids useful for peptidomimetics.

Synthesis and conformational analysis of peptides embodying 2,3-methanopipecolic acids

When 2,3-methanopipecolic acids replace a proline in peptides, a marked preference (42–92%) for thecisgeometry around the pipecolic amide bond is observed in both water and organic solvents.