The synthesis of (±)-crispine A in 9 steps and 24% overall yield
was achieved using a nitrosoalkene hetero-Diels-Alder addition
to ethyl vinyl ether as the key step. The synthesis starts from
commercial 3,4-dimethoxyphenylacetic acid and uses simple methods,
easily accessible materials and inexpensive reagents. An isochroman
derivative was unexpectedly formed in an attempted reduction of
a dihydro-4H-1,2-oxazine intermediate.
alkaloids - natural products - total synthesis - hetero-Diels-Alder reaction - hydrogenation