Preliminary Study of the Total Synthesis of Bao Gong Teng A Analogs Using 8-Benzyl-2-oxo-8-azabicyclo[3.2.1]oct-3-ene-6-endo/exo- and 7-endo/exo-carbonitrile

The use of four cycloadducts from the Katritzky reaction for subsequent preparation of Bao Gong Teng A analogs was studied. We show that the reduction of 2-oxo-8-azabicyclo[3.2.1]octanes (1-4) to alcohols allows the 2-exo/endo isomerism to be exploited. The 7-endo compound (4) also yielded azatricyclo[5.2.l.04,8]decanone (12) from alcohol (11). When the nitrile was converted into an acetyl group, 6-endo products (13) and (14) were isornerized to 6-exo. Trimethylsilyloxy derivatives (13-18) ultimately yielded 2-hydroxy-azabicyclooctethanone (22-24). These results afford an approach to the synthesis of the 6-exo 2-endo, 7-exo 2-exo and 7-exo 2-endo isomers of Bao Gong Teng A.