Cyclopropane ring-opening of tricyclo[3.3.0.02,8]octan-3-ones: a quick access to bicyclo[3.2.1]octanones from 2-methoxyphenols

Synthesis of new cyclazines and 4,5-diaryl-1H-pyrrol-3(2H)-one units in discoipyrroles from indolizinone-DMAD cycloadducts

The reaction of indolizinones with dimethyl acetylenedicarboxylate gave direct access to 3',8a-dihydrocyclopenta[hi]indolizin-8a-ol and 1H-pyrrol-3(2H)-one in good yields. The former skeleton is a precursor to cyclazines with nitrogen on the periphery, a hitherto un-accessed 10-π system. Their formation involves initial [4 + 2] or [8 + 2] modes of cycloadditions; the retro-Diels Alder reaction of the [4 + 2] cycloadduct leads to 1H-pyrrol-3(2H)-one, whereas [8 + 2] addition followed by π-reorganization leads to the azatricyle. Analysis of substituent effects on product distribution showed that electron donating groups on the C₃-aryl ring promote the formation of the azatricycle preponderantly. Treatment of one of these azatricycles (3c) with HBF₄ led to the formation of the corresponding 10e-aromatic species which was detected by NMR spectroscopy. In addition, formation of the 1H-pyrrol-3(2H)-one skeleton through the normal retro-Diels Alder pathway was employed in the total synthesis of Discoipyrrole C, which is a new lead against lung cancer.

Construction of the azocane (azacyclooctane) moiety of the Lycopodium alkaloid lycopladine H via an intramolecular hydroaminomethylation strategy

An efficient synthetic strategy has been developed for annulation of an azocane ring onto a bicyclo[2.2.2]octane scaffold via an intramolecular hydroaminomethylation protocol to generate an advanced intermediate bearing three of the four rings of the structurally unique Lycopodium alkaloid lycopladine H (1).

Exploratory studies towards a total synthesis of the unusual bridged tetracyclic Lycopodium alkaloid lycopladine H

A strategy for a total synthesis of the structurally novel Lycopodium alkaloid lycopladine H has been investigated. Key steps that have been tested include: 1.a regioselective Diels-Alder cycloaddition of nitroethylene with an o-quinone ketal to produce the bicyclo[2.2.2]octane moiety of the alkaloid; 2. a stereoselective Henry reaction to generate the requisite functionality and configuration at C-5; 3. a stereoselective catalytic hydrogenation of a trisubstituted alkene to set the C-15 methyl configuration.