4 research outputs found
Total Synthesis of (+)-Clavilactone A and (−)-Clavilactone B by Ring-Opening/Ring-Closing Metathesis
The enantioselective total synthesis of natural enantiomers of clavilactones A and B has been achieved. A key feature of the synthesis is the use of a ring-opening/ring-closing metathesis, which allows the one-pot transformation of a strained cyclobutenecarboxylate into a γ-butenolide
Total Synthesis of (+)-Vibsanin A
The
first total synthesis of (+)-vibsanin A, an 11-membered vibsane diterpenoid,
was achieved, unambiguously establishing its relative and absolute
stereochemistry. Highlights of the synthesis include the stereoselective
formation of an all-carbon quaternary stereocenter by a zinc-mediated
Barbier-type allylation in an aqueous medium, and the efficient construction
of an 11-membered ring skeleton by a combination of an intramolecular
Nozaki–Hiyama–Kishi (NHK) reaction and a Mitsunobu reaction
Enantioselective Total Synthesis of (−)-Misramine
The enantioselective total synthesis
of an unusual pentacyclic
proaporphine alkaloid, (−)-misramine, was achieved. The synthetic
strategy relied on an enantioselective intramolecular Friedel–Crafts-type
1,4-addition using an asymmetric organocatalyst to construct a spiroindane
skeleton containing an all-carbon quaternary stereocenter and a double
reductive amination of the keto-aldehyde to form a piperidine ring
toward the end of the synthesis. This work is the first example of
asymmetric synthesis of a proaporphine alkaloid
Total Synthesis of Clavilactones
Clavilactones
A, B, and D are epidermal growth factor receptor
tyrosine kinase inhibitors that were isolated from cultures of the
fungus <i>Clitocybe clavipes</i>. Here, we report full details
of the total synthesis of these clavilactones. A key feature of our
synthetic approach is a ring-opening/ring-closing metathesis strategy
that allows the concise transformation of a cyclobutenecarboxylate
into a γ-butenolide. Coupled with enantioselective Ti/BINOL-catalyzed
alkynylation of a multisubstituted benzaldehyde and ring-closing metathesis
of a diene-bearing silylene acetal to construct the 10-membered carbocycle,
this strategy enabled the total synthesis of the natural enantiomers
(+)-clavilactone A and (−)-clavilactone B. In addition, the
correct structure of clavilactone D was determined by the synthesis
of two newly proposed structures. This research resulted in the asymmetric
synthesis of the revised (+)-clavilactone D