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Speaker: Prof. Viresh H. Rawal
Department of Chemistry
University of Chicago
Chicago, IL 60637 USA
Title: "Unified Strategy for the Synthesis of Veratrum
Alkaloids: Convergent Assembly and Late-Stage
Skeletal Reorganization."
Date: Monday, August 17, 2026
Time: 17:00 hrs
Venue: P. C. Saxena Auditorium, IIT Bombay
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Abstract The synthesis of complex natural products is most rewarding when it transcends the
preparation of a single target and instead provides a strategic framework for accessing an
entire family of structurally related molecules. Such an approach requires identifying simplifying
transformations that rapidly build molecular complexity while also enabling divergence to
distinct structural types. It is with this objective that we undertook the synthesis of alkaloids
belonging to the Veratrum family, whose intricate C-nor-D-homo steroid skeletons and diverse
ring connectivities have challenged synthetic chemists for decades. In this presentation, I will
discuss the strategic and tactical considerations that guided our development of a unified, de
novo approach to these remarkable natural products. Central to this work is a convergent
strategy featuring a transition-metal-catalyzed [2 + 2 + 2] cycloisomerization that assembles
three rings of the cevanine framework in a single operation. I will first describe the synthesis of
(+)-heilonine, which established this general strategy and provided a versatile platform for
subsequent investigations. I will then discuss our efforts toward (–)-verarine, in which selective
late-stage bond ablation of the cevanine skeleton enabled efficient access to the
veratramine subclass of alkaloids. Finally, I will describe the synthesis of (+)-ussuriedine, where
a late-stage Stevens rearrangement forged the defining carbon–carbon bond of its
unprecedented azatricyclic framework while simultaneously providing a plausible hypothesis
for its biosynthesis. Collectively, these studies illustrate how the pursuit of complex molecule
synthesis can inspire unconventional strategic disconnections, and provide insights into natural
product biosynthesis.