Tandem allylboration-ring-closing metathesis reactions for the preparation
of biologically active molecules*
P. Veeraraghavan Ramachandran, M. Venkat Ram Reddy, and Herbert C.
Brown
Herbert C. Brown Center for Borane Research, Department
of Chemistry, Purdue University, West Lafayette, IN 47907, USA
Abstract: The development of asymmetric synthesis during the
past two decades aided organic chemists considerably in the synthesis
of complex natural products. Organoborane chemistry continues to play
an important role in asymmetric synthesis. One of the important reactions
that has become very common in the arsenal of synthetic chemists is
allylboration and related reactions. Another important reaction that
has recently attained enormous importance in organic chemistry is the
ring-closing metathesis (RCM) reaction. Indeed, a combination of allylboration
and RCM reactions provides an excellent route to cyclic ethers, lactones,
lactams, etc. Herein, we describe a sequential asymmetric allylboration
and RCM reaction protocol that has been utilized for the synthesis of
several alpha-pyrone-containing natural products,particularly biologically
active molecules.
*Lecture presented at the XIth International Meeting
on Boron Chemistry (IMEBORON XI), Moscow, Russia, 28 July - 2 August
2002. Other presentations are published in this issue,
pp. 1157-1355.
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