Adiastereoselective approach for the total synthesis of an unusual atropisomer of the Schisandratriterpenoid (AE)schiglautone Ai sd escribed. The efficient synthetic strategy features three key transformations:1)two sequential titanium-(III)-catalyzed radical cyclization/homologation reactions to construct the trans-fused [6,7] bicycle as well as install the quaternary carbons at C10 and C14 with the desired stereochemistry;2 )a Claisen rearrangement followed by ar ingclosing metathesis to forge the strained nine-membered ring; and 3) as ubstrate-controlled Michael addition to enable the introduction of the C17 side-chain with good diastereoselectivity.
Daphenylline is a structurally unique member of the triterpenoid Daphniphyllum natural alkaloids, which exhibit intriguing biological activities. Six total syntheses have been reported, five of which utilize aromatization approaches. Herein, we report a concise protecting-group-free total synthesis by means of a novel intramolecular oxidative dearomatization reaction, which concurrently generates the critical seven-membered ring and the quaternary-containing vicinal stereocenters. Other notable transformations include a tandem reductive amination/amidation double cyclization reaction, to assemble the cage-like architecture, and installation of the other two chiral stereocenters via a highly enantioselective rhodium-catalyzed challenging hydrogenation of the diene intermediate (90% e.e.) and an unprecedented remote acid-directed Mukaiyama−Michael reaction of the complex benzofused cyclohexanone (13:1 d.r.).
With the aid of a
class of newly discovered Trost-type bisphosphine
ligands bearing a chiral cycloalkane framework, the Pd-catalyzed decarboxylative
dearomative asymmetric allylic alkylation (AAA) of benzofurans was
achieved with high efficiency [0.2–1.0 mol% Pd2(dba)3/L], good generality, and high enantioselectivity
(>30 examples, 82–99% yield and 90–96% ee). Moreover,
a diversity-oriented synthesis (DOS) of previously unreachable flavaglines
is disclosed. It features a reliable and scalable sequence of the
freshly developed Tsuji–Trost–Stoltz AAA, a Wacker–Grubbs–Stoltz
oxidation, an intra-benzoin condensation, and a conjugate
addition, which allows the efficient construction of the challenging
and compact cyclopenta[b]benzofuran scaffold with
contiguous stereocenters. This strategy offers a new avenue for developing
flavagline-based drugs.
Jasmonates (JAs) play a key role in the regulation of growth and the defense response to environmental stresses. JAs inhibit plant growth and promote defense response. However, their roles in desert halophyte in the response to salt stress remain poorly understood. The effects of the combination of methyl jasmonate (MeJA) and NaCl treatment (the "MeN" condition) on the growth regulation and
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