We thank the National Institutes of
Health (GM 25439), Pfizer, Inc., Merck Research Laboratories,
and the Robert A. Welch Foundation for their generous
support of this research. We are grateful to Prof. Dirk Trauner
for providing copies of experimental procedures and spectral
data of several intermediates and to Prof. Chihiro Kibayashi
for providing us with copies of spectra of 4. We are also
grateful to Dr. Richard Fisher (Materia, Inc.) for catalyst
support and helpful discussions. An NIH Postdoctoral
Fellowship to R.B.A. is gratefully acknowledged.