Acknowledgment. We thank the NIH (N

Acknowledgment. We thank the NIH (NCI CA 10658, D.R. and J.W.S.; CA81713, J.W.S.) and the Welch Founda- tion (D.R.) for support of these investigations.

Supporting Information Available: Selected experi- mental procedures and characterization data (including 1H and 13C) for compounds 1-3, 4, 6, 7, 8a, 9a, 11, and 13. This material is available free of charge via the Internet at http://pubs.acs.org.