Substrate Specificity and Stereoselectivity of Two Sulfolobus 2‐Keto‐3‐deoxygluconate Aldolases towards Azido‐Substituted Aldehydes

Abstract

The 2‐keto‐3‐deoxygluconate aldolases (KDGAs) isolated from Sulfolobus species convert pyruvate and glyceraldehyde reversibly into 2‐keto‐3‐deoxygluconate and ‐galactonate. As a result of their high thermostability and activity on nonphosphorylated substrates, KDGA enzymes have potential as biocatalysts for the production of building blocks for fine chemical and pharmaceutical applications. Up to now, wild‐type enzymes have only shown moderate stereocontrol for their natural reaction. However, if a set of azido‐functionalized aldehydes were applied as alternative acceptors in the reaction with pyruvate, the stereoselectivity was strongly increased to give enantiomeric or diastereomeric excess values up to 97 %. The Sulfolobus acidocaldarius KDGA displayed a higher stereoselectivity than Sulfolobus solfataricus KDGA for all tested reactions. The azido‐containing products are useful chiral intermediates in the synthesis of nitrogen heterocycles.

Biocatalytic routes to anti-viral agents and their synthetic intermediates

“…Chem 2-azidoacetaldehyde and pyruvate in a stereoselective fashion. 255 Zinc-catalysed deprotection and reduction resulted in the generation of hydroxyproline as a mixture of diastereomers in which the undesired (4S)-isomer prevailed. Hydroxylation of L-proline is thus the preferred route to the desired (2S,4R)-hydroxyproline isomer.…”

“…Scheme 50 Transaminase (ATA-117)-catalysed synthesis of (R)-3-aminobutanoate. 294 306 Modern-day neuraminidase inhibitors such as oseltamivir (254), zanamivir (255) and peramivir (256), act as mimics of this sialosyl cation. 307 3.6.1 Oseltamivir.…”

Structurally Informed Mutagenesis of a Stereochemically Promiscuous Aldolase Produces Mutants That Catalyze the Diastereoselective Syntheses of All Four Stereoisomers of 3-Deoxy-hexulosonic Acid

“… 24 Interestingly, use of l -glyceraldehyde acetonide as a substrate resulted in an aldol reaction with opposing diastereoselectivity, affording a mixture of l -KDGlc and l -KDGal in 3:97 dr, thus indicating that the facial selectivity of both these aldol reactions occurs under enzymatic control ( Figure 1 e). 24 , 28 …”

“…Subsequent evaluation of aldolase crystal structures containing d -KDGlc and d -KDGal led us to consider using a more rigid cyclic d -glyceraldehyde acetonide substrate, which resulted in a highly diastereoselective aldol reaction that produced d -KDGlc and d -KDGal in 96:4 dr (Figure d) . Interestingly, use of l -glyceraldehyde acetonide as a substrate resulted in an aldol reaction with opposing diastereoselectivity, affording a mixture of l -KDGlc and l -KDGal in 3:97 dr, thus indicating that the facial selectivity of both these aldol reactions occurs under enzymatic control (Figure e). , …”