Total synthesis of (-)-norzoanthamine.

No bones about it: (-)-Norzoanthamine, a promising candidate for an anti-osteoporotic drug, was the target of a total synthesis (see scheme). The final bisaminal formation with AcOH/H(2)O gave the DEFG ring, while the cyclization precursor was prepared by installing the remaining bisaminal unit after oxidative cleavage of the cyclopentanol moiety.