Complete integration of carbene-transfer chemistry into biosynthesis

Nature. 2023 May;617(7960):403-408. doi: 10.1038/s41586-023-06027-2. Epub 2023 May 3.


Biosynthesis is an environmentally benign and renewable approach that can be used to produce a broad range of natural and, in some cases, new-to-nature products. However, biology lacks many of the reactions that are available to synthetic chemists, resulting in a narrower scope of accessible products when using biosynthesis rather than synthetic chemistry. A prime example of such chemistry is carbene-transfer reactions1. Although it was recently shown that carbene-transfer reactions can be performed in a cell and used for biosynthesis2,3, carbene donors and unnatural cofactors needed to be added exogenously and transported into cells to effect the desired reactions, precluding cost-effective scale-up of the biosynthesis process with these reactions. Here we report the access to a diazo ester carbene precursor by cellular metabolism and a microbial platform for introducing unnatural carbene-transfer reactions into biosynthesis. The α-diazoester azaserine was produced by expressing a biosynthetic gene cluster in Streptomyces albus. The intracellularly produced azaserine was used as a carbene donor to cyclopropanate another intracellularly produced molecule-styrene. The reaction was catalysed by engineered P450 mutants containing a native cofactor with excellent diastereoselectivity and a moderate yield. Our study establishes a scalable, microbial platform for conducting intracellular abiological carbene-transfer reactions to functionalize a range of natural and new-to-nature products and expands the scope of organic products that can be produced by cellular metabolism.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, N.I.H., Extramural

MeSH terms

  • Azaserine* / biosynthesis
  • Azaserine* / chemistry
  • Biocatalysis
  • Biological Products / chemistry
  • Biological Products / metabolism
  • Coenzymes / chemistry
  • Coenzymes / metabolism
  • Cyclopropanes / chemistry
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism
  • Multigene Family / genetics
  • Styrene / chemistry


  • Azaserine
  • carbene
  • Biological Products
  • Styrene
  • Cyclopropanes
  • Coenzymes
  • Cytochrome P-450 Enzyme System

Supplementary concepts

  • Streptomyces albus