Ap ractical chemoenzymatic method for the synthesis of 9-hydroxynonanoic acid and1 ,9-nonanedioic acid (i.e., azelaic acid) from oleic acid [(9Z)-octadec-9-enoic acid] was investigated. Biotransformation of oleic acid into 9-(nonanoyloxy)nonanoic acid via 10-hydroxyoctadecanoic acid and 10keto-octadecanoic acid was driven by aC -9 double bond hydratase from Stenotrophomonas maltophilia, an alcohol dehydrogenase from Micrococcus luteus, and aB aeyer-Villiger monooxygenase (BVMO) from Pseudomonas putida KT2440, which was expressedi nr ecombinant Escherichia coli.A fter productiono ft he ester (i.e. ,t he BVMO reactionp roduct), the compound wasc hemically hydrolyzed to nnonanoic acid and9 -hydroxynonanoic acid because n-nonanoic acid is toxic to E. coli.T he ester was also converted into 9-hydroxynonanoic acid and the n-nonanoic acid methyle ster, which can be oxygenated into the 9-hydroxynonanoic acid methyl ester by the AlkBGT from P. putida GPo1. Finally,9 -hydroxynonanoic acid was chemically oxidized to azelaic acid with ah ighy ield under fairly mild reactionc onditions.F or example,w hole-cell biotransformation at ah igh cell density (i.e., 10 gd ry cells/L) allowed the final ester product concentration and volumetric productivity to reach2 5mMa nd 2.8 mM h À1 ,r espectively.T he overall molar yield of azelaic acid from oleic acid was 58%, based on the biotransformation and chemical transformation conversion yields of 84% and 68%, respectively.Scheme 2. Chemical conversion of the ester intermediate (4)toa zelaic acid (7).

Halogen bonding has been used to glue together hydrogen‐bonded short arylamide foldamers to achieve new supramolecular double and quadruple helices in the solid state. Three compounds, which bear a pyridine at one end and either a CF2I or fluorinated iodobenzene group at the other end, engage in head‐to‐tail N⋅⋅⋅I halogen bonds to form one‐component supramolecular P and M helices, which stack to afford supramolecular double‐stranded helices. One of the double helices can dimerize to form a G‐quadruplex‐like supramolecular quadruple helix. Another symmetric compound, which bears a pyridine at each end, binds to ICF2CF2I through N⋅⋅⋅I halogen bonds to form two‐component supramolecular P and M helices, with one turn consisting of four (2+2) molecules. Half of the pyridine‐bearing molecules in two P helices and two M helices stack alternatingly to form another supramolecular quadruple helix. Another half of the pyridine‐bearing molecules in such quadruple helices stack alternatingly with counterparts from neighboring quadruple helices, leading to unique quadruple helical arrays in two‐dimensional space.

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