While it is unclear exactly why the presence of Ti(0-i- Pr)4 provides such a strong tendency for 2,3-epoxy acids and secondary amides to be opened by nucleophiles at C-3, the observed regioselectivities may be rationalized by proposing the formation of an intermediate titanium complex such as 18. Opening at C-3 occurs preferentially PY ... Acknowledgment. We thank the National Science Foundation (CHE-8308355) and Merck and Company for generous support of this ...