A new versatile and diastereoselective synthesis of polysubstituted 2-oxopiperazines from naturally occurring amino acids

Efficient synthesis of 5-(hydroxymethyl)piperazin-2-ones using automatically prepared chiral bromocarboxylic acid and Garner's aldehyde as versatile building blocks

An efficient method for the synthesis of substituted 5-(hydroxymethyl)piperazin-2-ones was established by using an automated synthesis process. Thirteen piperazinones were synthesized from chiral α-bromocarboxylic acids and Garner's aldehyde which were prepared by using our originally developed automated synthesizer, ChemKonzert®. The automated method of synthesizing chiral α-bromocarboxylic acids was efficient and safe because the rate of the dropwise addition of the reagent can be controlled using the automated synthesizer. This method is expected to contribute to the synthesis of pharmaceuticals.

Structure-Activity Relationship Studies on Oxazolo[3,4-a]pyrazine Derivatives Leading to the Discovery of a Novel Neuropeptide S Receptor Antagonist with Potent In Vivo Activity

Neuropeptide S modulates important neurobiological functions including locomotion, anxiety, and drug abuse through interaction with its G protein-coupled receptor known as neuropeptide S receptor (NPSR). NPSR antagonists are potentially useful for the treatment of substance abuse disorders against which there is an urgent need for new effective therapeutic approaches. Potent NPSR antagonists in vitro have been discovered which, however, require further optimization of their in vivo pharmacological profile. This work describes a new series of NPSR antagonists of the oxazolo[3,4-a]pyrazine class. The guanidine derivative 16 exhibited nanomolar activity in vitro and 5-fold improved potency in vivo compared to SHA-68, a reference pharmacological tool in this field. Compound 16 can be considered a new tool for research studies on the translational potential of the NPSergic system. An in-depth molecular modeling investigation was also performed to gain new insights into the observed structure-activity relationships and provide an updated model of ligand/NPSR interactions.

Amino acid chirons: a tool for asymmetric synthesis of heterocycles

As a result of their easy availability in enantiomerically enriched form and their possession of synthetically transformable diverse functional groups, amino acids have been extensively used by synthetic organic and medicinal chemists as a chiral pool for access to heterocycles (monocycles, bicycles or polycycles, either bridged or fused). This review describes the syntheses of diverse asymmetric heterocycles with various membered rings (n = 3-9) followed by benzo or heteroannulated ones, for the period from 1996 to Dec. 2013. It details solution phase synthetic methodologies in which the naturally occurring α-amino acid is incorporated, totally or partially, into the final product.

Stereoselective synthesis of 3-substituted tetrahydropyrazinoisoquinolines via intramolecular cyclization of enantiomerically enriched dihydro-2H-pyrazines

The preparation of 3-substituted tetrahydropyrazinoisoquinolines using the tributyltin hydride mediated intramolecular radical cyclization of suitably protected 2-substituted 3,4-dihydropyrazines is reported. The compounds are obtained as single enantiomers, as the relative configuration of the new generated stereogenic center is driven by the stereochemistry of the 2-substituted carbon in the starting materials, which is in turn derived from naturally occurring amino acids.