Enzymatic methods for the oxidation of alcohols are critically reviewed. Dehydrogenases and oxidases are the most prominent biocatalysts, enabling the selective oxidation of primary alcohols into aldehydes or acids. In the case of secondary alcohols, region and/or enantioselective oxidation is possible. In this contribution, we outline the current state-of-the-art and discuss current limitations and promising solutions.

The total syntheses of three enantiomerically pure non-proteinogenic amino acids, l-norvaline, γ-oxonorvaline, and syn-γ-hydroxynorvaline, are reported. The chromatography-free route pivoted on the construction of highly enantiomerically enriched substituted α-amino-γ-oxopentanoic acid, from which all three members were accessed divergently via chemoselective and stereoselective reductions. The rapid synthesis of this key α-amino-γ-oxopentanoic acid was achieved by a highly diastereoselective crystallisation-driven three-component Mannich reaction from the readily available building blocks acetone, glyoxylic acid monohydrate, and (S)-(4-methoxyphenyl)ethylamine. The enantiomeric purity of all target molecules was confirmed by HPLC analysis, either of the amino acids or their derivatives.

This comprehensive review of filbertone, a principal flavor compound of hazelnut, evaluates the current state of the art of all relevant aspects of the title molecule: its occurrence and properties, laboratory preparation and bulk synthesis, analytical issues regarding stereochemistry and purity, sensory evaluation, and practical uses. Comparisons are made between different synthetic approaches, and a critical assessment of various applications is presented.

A practical synthetic strategy for the preparation of enantiomerically pure 3‐substituted pyroglutamic acid derivatives is described. This procedure pivots on fast 5‐exo‐tet cyclization of the chloroacetylated amino acids, prepared by the crystallization induced diastereomeric transformations (CIDT). Furthermore, oxidation of obtained 3‐substituted pyroglutamic acids afforded highly valuable scaffolds with a quaternary stereogenic center with excellent diastereoselectivity. The absolute stereochemical configuration of both, 3‐aroyl pyroglutamic acid and its 3‐hydroxylated derivative, was confirmed by single‐crystal X‐ray analysis. The versatility of the methodology is exemplified using a variety of aromatic and heteroaromatic amino acids. The efficiency of this chromatography‐free approach predestines it for the gram‐scale synthesis. This was demonstrated with the synthesis of more than 10 mmol of the model substrate with excellent overall yield and diastereoselectivity.

Non-enantioselective alcohol dehydrogenases (ADHs) are rarely found in the biocatalysis portfolio. Generally, highly enantioselective ADHs are sought for. Using such ADHs for the oxidation of racemic alcohols generally results in a kinetic resolution of the starting material, which is unfavourable if the ketone represents the product of interest. In the current contribution we report the ADH from Sphingobium yanoikuyae (SyADH) as non-enantioselective ADH for the complete oxidation or rac-heptan-2-ol (representing further 2-alkanols).