4 research outputs found
Development of Solid- and Solution State NMR Spectral Simplification Methods for Complex Organic Molecules
Nazarov Cyclization and Tandem [4 + 2]-Cycloaddition Reactions of Donor–Acceptor Cyclopropanes
The development of aryl vinyl/divinyl
donor–acceptor cyclopropanes
(DACs) as novel Nazarov cyclization (NC) precursors is described.
The 1,3-zwitterion, generated from DACs embedded in the divinyl framework,
acts as a pentadienyl cation, a requisite for Nazarov cyclization.
A cyclic allyl cation in the course of NC was trapped with external
nucleophiles to provide an interrupted NC product. Indeed, an allyl
cation in this reaction is analogous to a 1,4-zwitterion that on reaction
with dipolarophiles provided an easy access to substituted pyrans
with excellent yield and diastereoselectivity via NC followed by a
formal [4 + 2] cycloaddition
Stereoselective Access to the Core Structure of Macroline-Type Indole Alkaloids: Total Synthesis of Macroline and Alstomicine
Rapid
synthesis of the pentacyclic core structure of macroline-type
indole alkaloids, and its application in the total synthesis of macroline
and alstomicine is described. The core structure was accomplished
in a highly stereocontrolled manner via two key steps, Ireland–Claisen
rearrangement and Pictet–Spengler cyclization, commencing from
a readily available starting material l-tryptophan, which
obviated the need of a particular chiral source as an external catalyst,
reagent, or internal auxiliary