Ahmad, Sajjad
(2012)
One-pot tandem reactions for the stereoselective synthesis of functionalised carbocycles.
PhD thesis, University of Glasgow.
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Abstract
A one-pot, two step tandem process involving an Overman rearrangement and a ring
closing metathesis reaction has been utilised for the efficient synthesis of various cyclic
allylic trichloroacetamides from simple allylic alcohols. Various methods were then
investigated for the allylic oxidation of a carbocyclic amide using TBHP along with
different transition metals such as Pd, Se, Mn and Cr. This was required for the synthesis
of the important building blocks for the construction of structurally diverse antiviral and
anticancer carbocyclic nucleosides and natural products.
The oxidation of (1S)-N-(cyclohexenyl)trichloroacetamide was then studied leading to the
preparation of two diol analogues in excellent stereoselectivity. The cyclohexene
derivative was also stereoselectively functionalised using Upjohn dihydroxylation
conditions or by a directed epoxidation/hydrolysis sequence of reactions to generate two
aminocyclitols, the enantiomer of dihydroconduramine C-1 and dihydroconduramine E-1
in excellent stereoselectivity.
In addition to this, a one-pot tandem process involving a substrate-directed Overman
rearrangement and ring closing metathesis reaction was developed for the stereoselective
synthesis of a functionalised carbocyclic allylic trichloroacetamide. The functionalised
carbocyclic amide was employed in the successful synthesis of a syn-(4aS,10bS)-
phenanthridone framework using a Pd-catalysed cross-coupling reaction. Stereoselective
epoxidation and dihydroxylation of the syn-(4aS,10bS)-phenanthridone was then
investigated leading to the preparation of new analogues of 7-deoxypancratistatin.
Attempts were also made to use the functionalised carbocyclic amide in the total synthesis
of the Amaryllidaceae alkaloid (+)-γ-lycorane.
Further studies were then investigated to expand the scope of the one-pot tandem process
to include heterocyclic derived substrates. This led to a seven-membered carbocyclic
amide, which has been modified to create a diastereomeric core of balanol.
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