The formose reaction, one of the oldest name reactions in organic chemistry, uses formaldehyde as a C1 unit resulting in different monosaccharides and sugar‐like compounds. Nucleophilic formyl elongation is an attractive option to obtain 1,2‐functionalised building blocks for organic synthesis and pharmaceuticals; however, it has rarely been applied in asymmetric catalysis. The thiamine diphosphate dependent enzyme 2‐keto acid decarboxylase (KdcA) from Lactococcus lactis is able to transfer formyl units to aliphatic and aromatic aldehydes, both in an electrophilic and in a nucleophilic way. We have established the formation of unstable chiral 2‐hydroxy aldehydes by subsequent modifications (chemical derivatisation with 2,4‐dinitrophenylhydrazine, (R)‐Mosher's acid chloride) or by enzymatic trapping (oxidation and reductive amination).

This review provides an overview of different C1 building blocks as substrates of enzymes, or part of their cofactors, and the resulting­ functionalized products. There is an emphasis on the broad range of possibilities of biocatalytic one-carbon extensions with C1 sources of different oxidation states. The identification of uncommon biosynthetic strategies, many of which might serve as templates for synthetic or biotechnological applications, towards one-carbon extensions is supported by recent genomic and metabolomic progress and hence we refer principally to literature spanning from 2014 to 2020.1 Introduction2 Methane, Methanol, and Methylamine3 Glycine4 Nitromethane5 SAM and SAM Ylide6 Other C1 Building Blocks7 Formaldehyde and Glyoxylate as Formaldehyde Equivalents8 Cyanide9 Formic Acid10 Formyl-CoA and Oxalyl-CoA11 Carbon Monoxide12 Carbon Dioxide13 Conclusions

Highly functionalized polyol building blocks have been synthesized by means of stereoselective chemoenzymatic C–C bond formation followed by stereoselective reduction. Catalysis by thiamine diphosphate (ThDP) dependent benzaldehyde lyase (BAL) with glyceraldehyde acetonide as acceptor substrate gave highly stereoenriched polyols such as (1S,2S,3R)‐1‐phenylbutane‐1,2,3,4‐tetrol (1), the 3,4‐protected anti‐1,2‐diol 5, and the precursor of both compounds, 2‐hydroxyketone 4.

S-Adenosyl-L-homocysteine hydrolase (SAHH) reversibly cleaves S-adenosyl-L-homocysteine (SAH), the product of S-adenosyl-L-methionine (SAM) dependent methylation reactions. The conversion of SAH into adenosine and L-homocysteine (Hcy) plays an important role in the regulation of the methyl cycle. An alternative metabolic route for SAM regeneration in the extremophiles Methanocaldococcus jannaschii and Thermotoga maritima was identified with the deamination of SAH to S-inosyl-L-homocysteine (SIH). Herein, we report the first structural characterisation of different archaeal SAHHs together with a biochemical analysis of various SAHHs from all three domains of life. We found that homologues deriving from the Euryarchaeota phylum show a higher conversion rate with SIH compared to SAH. Crystal structures of SAHH originating from Pyrococcus furiosus in complex with SIH and inosine as ligands, show architectural flexibility in the active site and offer deeper insights into the binding mode of hypoxanthine-containing substrates. Altogether, the findings presented in this study support the understanding of an alternative metabolic route for SAM and offer insights into the evolutionary progression and diversification of SAHHs involved in methyl and purine salvage pathways.

Polystyrolproben werden mit Eisen(III)chlorid und weißen LEDs zu Oligomeren und Benzoylprodukten; ein Wolframatkatalysator invertiert die Absolutkonfiguration an sp3‐Kohlenstoffzentren; gelöstes Rätsel um eine symmetrieverbotene konrotatorische 14‐Elektronen‐Elektrocyclisierung; Polycarbonate, die sich ohne Lösungsmittel recyceln lassen: Highlights von Oktober 2021 bis 2022.