Modular Chemoenzymatic Synthesis of GE81112 B1 and Related Analogues Enables Elucidation of Its Key Pharmacophores

Abstract

The GE81112 complex has garnered much interest due to its broad antimicrobial properties and unique ability to inhibit bacterial translation initiation. Herein we report the use of a chemoenzymatic strategy to complete the first total synthesis of GE81112 B1. By pairing iron and α-ketoglutarate dependent hydroxylases found in GE81112 biosynthesis with traditional synthetic methodology, we were able to access the natural product in 11 steps (longest linear sequence). Following this strategy, 10 GE81112 B1 analogues were synthesized, allowing for identification of its key pharmacophores. A key feature of our medicinal chemistry effort is the incorporation of additional biocatalytic hydroxylations in modular analogue synthesis to rapidly enable exploration of relevant chemical space.

Scalable and Selective β‐Hydroxy‐α‐Amino Acid Synthesis Catalyzed by Promiscuous l‐Threonine Transaldolase ObiH

“…Notably, the enantioselectivity of ObiH-catalyzed reactions is high (> 99 % ee for all products). Phenylserine analogs generated under these conditions include p-chloro-phenylserine (18), p-bromo-phenylserine (19) and m-bromo-phenylserine (20). To unambiguously assign the absolute configuration of ObiH-generated product 18, the compound was recrystallized and characterized by small-molecule X-ray diffraction.…”

“…[47,48] While biosynthetic strategies which involve late stage selective hydroxylation have found success in generating aliphatic β-hydroxy-α-amino acid, this approach is highly substrate specific and precludes a generalized route to simultaneously install a diverse variety of side chains and the β-hydroxyl group. [18,19] ObiH-catalyzed aldol reactions therefore offer a streamlined enzymatic route to access diverse β-hydroxy-α-amino acid.…”

“…In Nature, the β-hydroxy functional group is often installed on a pre-assembled amino acid through site-selective oxidation by cytochromes P450 or α-ketoglutarate dependent non-heme iron enzymes. [16][17][18][19] However, the ability to assemble the side chain while simultaneously setting the stereochemistry of the β-hydroxy group offers a more versatile, complementary approach for the preparative scale synthesis of structurally diverse non-standard amino acids (nsAAs). Researchers have therefore been drawn to the pyridoxal phosphate (PLP)dependent threonine aldolases (TAs) and serine hydroxymethyl transferases (SHMTs) for synthesis of β-hydroxy-α-amino acids.…”

Stereoselective Syntheses of Deuterated Pipecolic Acids as Tools to Investigate the Stereoselectivity of the Hydroxylase GetF

“…[4][5][6] The understanding of the biosynthetic route enabled a recent chemoenzymatic synthesis of congener B1 including a panel of derivatives. [7] The ensuing structure-activity relationship (SAR) study revealed the key pharmacophore of the structure. Among the key chemical moieties, the hydroxyl group of the 3-hydroxypipecolic acid moiety (3-HyPip) is essential for activity.…”

Hot off the press

“…28 This process identied biocatalysts capable of accepting a range of ketone The chemoenzymatic total synthesis of the antimicrobial peptide GE81112 B1 29 and 10 synthetic analogues has been reported. 29 Access to key building blocks utilised the stereoselective hydroxylation of L-pipecolic acid (Scheme 3) and Lcitrulline, using iron and a-ketoglutarate dependent dioxygenase enzymes. A one-pot two-step biocatalytic method for the stereoselective synthesis of vicinal diols has been developed.…”