posted on 2024-01-06, 14:07authored byQingyun Tang, Mark Petchey, Benjamin Rowlinson, Thomas J. Burden, Ian J. S. Fairlamb, Gideon Grogan
The synthesis of
amide bonds is one of the most frequently performed
reactions in pharmaceutical synthesis, but the requirement for stoichiometric
quantities of coupling agents and activated substrates in established
methods has prompted interest in biocatalytic alternatives. Amide
Bond Synthetases (ABSs) actively catalyze both the ATP-dependent adenylation
of carboxylic acid substrates and their subsequent amidation using
an amine nucleophile, both within the active site of the enzyme, enabling
the use of only a small excess of the amine partner. We have assessed
the ability of an ABS from Streptoalloteichus hindustanus (ShABS) to couple a range of carboxylic acid substrates and amines
to form amine products. ShABS displayed superior activity to a previously
studied ABS, McbA, and a remarkable complementary substrate specificity
that included the enantioselective formation of a library of amides
from racemic acid and amine coupling partners. The X-ray crystallographic
structure of ShABS has permitted mutational mapping of the carboxylic
acid and amine binding sites, revealing key roles for L207 and F246
in determining the enantioselectivity of the enzyme with respect to
chiral acid and amine substrates. ShABS was applied to the synthesis
of pharmaceutical amides, including ilepcimide, lazabemide, trimethobenzamide,
and cinepazide, the last with 99% conversion and 95% isolated yield.
These findings provide a blueprint for enabling a contemporary pharmaceutical
synthesis of one of the most significant classes of small molecule
drugs using biocatalysis.