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Chiral α-alkyl α-glycine acids are prevalent structural motifs found in pharmaceuticals and natural products, making them a significant dimension for exploration in modern pharmaceutical and medicinal chemistry. However, the current synthesis methods for these compounds face numerous environmental and practical challenges, highlighting the critical need to establish more sustainable approaches. Herein, we report the first liquid assisted grinding (LAG)-facilitated aerobic asymmetric cross-dehydrogenative coupling reaction involving glycine esters/amides and simple ketones/aldehydes, using a chiral amine catalyst under metal-free and solvent-minimal conditions. A wide variety of α-alkyl α-amino acid derivatives, containing two or three stereocenters, were generated in good yields with remarkable enantioselectivity and diastereoselectivity. Moreover, we propose a new enantioselective control model for mechanical ball milling, suggesting that stoichiometric EtOH may enhance the enantioselectivity by potentially interacting with both the catalyst and the imine ion intermediate. This method, closely aligned with the principles of green chemistry, offers a recoverable catalyst/grinding-aid system, has broad substrate compatibility, and enables the synthesis of multifunctionalized products suitable for diverse transformations, notably including the production of the unnatural amino acid L-cyclohexylglycine (a key intermediate in telaprevir synthesis). [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Ethanol-assisted mechanochemical asymmetric cross-dehydrogenative coupling reaction with recoverable chiral amine/NaCl for accessing chiral α-alkyl α-glycine derivatives" published in the journal Green Chemistry. The authors acknowledge inaccuracies in the mechanism and associated discussion in the original article. They provide a corrected scheme and clarify a sentence within the main article. The Royal Society of Chemistry apologizes for the errors. The document also includes information about the authors' affiliations and contact details. [Extracted from the article]

The autotrophic acetogen Clostridium ljungdahlii has emerged as a major candidate in the biological conversion of one-carbon gases (CO2/CO) to bulk chemicals and fuels. Nevertheless, the regulatory pathways and downstream metabolic changes responsible for product formation and distribution in this bacterium remain minimally explored. Protein lysine acetylation (PLA), a prevalent posttranslational modification, controls numerous crucial cellular functions. Herein, we revealed a novel cross-regulatory mechanism that uses both the PLA system and transcription factors to regulate the carbon flow distribution for product formation in C. ljungdahlii. The dominant acetylation/deacetylation system (At2/Dat1) in C. ljungdahlii was found to regulate the ratio of two major products, acetic acid and ethanol. Subsequent genetic and biochemical analyses revealed that the activities of Pta and AdhE1, two crucial enzymes responsible for acetic acid and ethanol synthesis, respectively, were greatly affected by their levels of PLA. We found that the acetylation statuses of Pta and AdhE1 underwent significant dynamic changes during the fermentation process, leading to differential synthesis of acetic acid and ethanol. Furthermore, the crucial redox-sensing protein Rex was shown to be regulated by PLA, which subsequently altered its transcriptional regulation on genes responsible for acetic acid and ethanol formation and distribution. Based on our understanding of this cross-regulatory module, we optimized the ethanol synthetic pathway by modifying the acetylation status (deacetylation-mimicked mutations of crucial lysine residues) of the related key enzyme, achieving significantly increased titer and yield of ethanol, an important chemical and fuel, by C. ljungdahlii in gas fermentation. [ABSTRACT FROM AUTHOR]