A highly enantioselective synthesis of sitagliptin, a potent DPP‐4 inhibitor, is reported. Explicitly identified chiral FerroLANE ligands in the presence of rhodium catalyze the asymmetric hydrogenation of an enamine to yield sitagliptin with excellent enantioselectivity (98% ee). The process was scaled up to 5 g and the final product was isolated as a phosphate salt with >99% ee.
Polyethylene is a highly apolar polymer with very poor
adhesion
to most substrates, necessitating the use of tie layers. Therefore,
the synthesis of functional polyethylene is a long-standing challenge
in catalytic ethylene polymerization. Here, we report the preparation
of a nanocomposite comprising polyethylene covalently grafted onto
sheet-like silsesquioxanes, with unprecedented adhesion to metal and
glass. A norbornene-grafted, layered Mg-silsesquioxane is treated
with Grubbs second-generation catalyst (G-II), and the identity of
covalently tethered G-II is unambiguously ascertained. Covalently
tethered G-II catalyzes the ring opening metathesis polymerization
of cyclooctene to poly(cyclooctene). The resulting poly(cyclooctene)
is catalytically hydrogenated to yield polyethylene. This polyethylene
nanocomposite exhibited a bonding strength of the order of 100 MPa
on stainless steel and aluminum, 10-fold higher than reported for
engineered polyethylene copolymers. The nanocomposite exhibits an
increase in the polar component of surface energy, yet remains compatible
and cocrystallizes with a polyethylene matrix.
Diabetes is on the rise across the Globe and millions of people are being affected. Sitagliptin has emerged as a potent inhibitor for the treatment of type II diabetes, which can regulate blood sugar level, and new strategies to prepare this molecule are being discovered. Herein we report a highly enantioselective synthesis of sitagliptin. Using specifically identified chiral FerroLANE ligands in the presence of a rhodium catalyst the asymmetric hydrogenation of an enamine to yield sitagliptin with excellent enantioselectivity (98% ee). The final product has been isolated as a phosphate salt with >99% ee. More information can be found in the Full Paper by Samir Chikkali et al. on page 189 in Issue 2, 2020 (DOI: 10.1002/ajoc.201900709).
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