Multifunctionality of the N -Trichloroacetyl Group Developed in the Synthesis of Tetrodotoxin, a Puffer Fish Toxin

This account describes a serendipitous discovery and the development of unique reactions associated with trichloroacetamide during synthetic studies of tetrodotoxin in our laboratory. The reactions include site-selective hydroxylation using the neighboring-group participation of trichloroacetamide, guanidinylation from a trichloroacetamide, protecting-group transformation, and removal of the N-trichloroacetyl group. These studies indicate the importance of the total synthesis of densely functionalized natural products as a field for the development of new reactions. 1 Introduction 2 Improvement of the Conditions for the Overman Rearrangement to Introduce Trichloroacetamide 3 Site-Selective Hydroxylation Using the Neighboring-Group Participation of Trichloroacetamide 4 Guanidine Synthesis 5 Protecting-Group Transformation of the N-Trichloroacetyl Group 6 New Deprotection Conditions for the Removal of the N-Trichloroacetyl Group 7 Conclusion.