Organocatalytic Syntheses of Bioactive Natural Products
135
Scheme 9. Synthesis of a collection of lepidopteran pheromones
4
N-Heterocycles
In the early stages of the UCS1025A campaign, we developed a novel
two-step approach to small N-heterocycles using an organocatalytic
Mannich reaction and a novel CDI-mediated dehydrative cyclization
(Münch et al. 2004). In the first step, we either used two identical aldehydes as the donor and the acceptor (Mannich dimerization) or an enolizable and a non-enolizable aldehyde (three-component Mannich reaction) followed by in situ reduction of the aldehyde function. In the
second step, the hydroxyl group was displaced by the amino group to
give the desired azetidines. As an example, we synthesized an analogue
of the cholesterol reducing drug ezetimibe (de Figueiredo et al. 2006).
135
Scheme 9. Synthesis of a collection of lepidopteran pheromones
4
N-Heterocycles
In the early stages of the UCS1025A campaign, we developed a novel
two-step approach to small N-heterocycles using an organocatalytic
Mannich reaction and a novel CDI-mediated dehydrative cyclization
(Münch et al. 2004). In the first step, we either used two identical aldehydes as the donor and the acceptor (Mannich dimerization) or an enolizable and a non-enolizable aldehyde (three-component Mannich reaction) followed by in situ reduction of the aldehyde function. In the
second step, the hydroxyl group was displaced by the amino group to
give the desired azetidines. As an example, we synthesized an analogue
of the cholesterol reducing drug ezetimibe (de Figueiredo et al. 2006).