Chemical Bonding: Happy hour in Havenmeyer

by Paul Hond
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Illustration by Richard BorgeBy the end of Commencement Week, the Morningside campus, which had been covered with aluminum bleachers, white tents, and more than 30,000 people, wore the trampled, sodden look of a fairground the morning after. On South Lawn, workers rolled up rubber mats, revealing a carpet of yellow straw where green turf had been. The disassembled metal benches on Low Plaza lay rain-flecked, gleaming dully. On Friday afternoon, few people were about, and the campus, recuperating from its hangover, was peaceful.

Any wanderer straying into Havemeyer Hall, then, perhaps to relax for a moment in the wooden splendor of the famous lecture hall, or to examine, under the display case, the century-old milk-testing equipment of chemistry department founder Charles F. Chandler, would have been surprised to find, on a bulletin board in an empty corridor, a flyer announcing an event at 4:00 p.m.

“Enantioselective Formal aza-Diels-Alder Reactions”

Presented by Sharon Lee (Leighton Group)

Highly functionalized piperidines represent an important class of heterocycles that are found in natural products and medicinally active agents. As a direct result, efforts to develop enantioselective diene-imine (aza-Diels-Alder) reactions to efficiently access these substructures have increased. We have developed highly enantioselectivesilicon Lewis acid mediated formal aza-Diels-Alder reactions with Danishefsky’s diene and non-Danishefsky’s diene to generate these biologically important heterocycles. To further prove the power of this method to access complex piperidine structures, we have accomplished the efficient synthesis of the drug target casopitant. During the course of our studies with aza-Diels-Alder reactions, we also became interested in natural products containing highly functionalized piperidines, in particular, the indolealkaloid Roxburghine D, due to its complex eight-fused ring system and four stereocenters. In the more than 40 years since its isolation, only one racemicsynthesis has beenreported. We hope to address this lack in an enantioselectivesynthesis through the use of a developed silicon Lewis acid mediated Pictet-Spengler reaction.

Room 209 Havemeyer
Happy Hour to follow!

Did someone say Happy Hour? Oh, for precious enzymes and sugars, for the pot of gold at the rainbow’s end! And really, what better way to draw a crowd to an hour-long talk about aza-Diels-Alder reactions on a Friday afternoon?

Conveniently, the post-talk bash was to be held upstairs on the seventh floor, in Havemeyer Lounge. No need for Dr. Chandler’s milk-testing apparatus here.

But first, business. At 4:00, Sharon Lee, a fourth-year doctoral candidate, greeted her audience in room 209. This was Lee’s first formal talk, and the tiered seats were filled with 40 of her colleagues in the graduate chemistry program, including her lab professor, James Leighton, assistant professor Scott Snyder, professor emeritus Gilbert Stork, and, on a central perch, the owlish eminence of professor Ronald

Breslow, now in his 55th year at Columbia. Lee, armed with a PowerPoint clicker and a matter-of-fact style, betrayed no flutters as she explained the stick-figure molecular schemes on the screen in language incomprehensible to most anyone outside Havemeyer — and even to some in it.

Also in the audience was Jonathan Owen, a 34-year-old assistant professor who had just been awarded a U.S. Department of Energy Early Career Research Grant. Owen’s lab studies the inorganic chemistry of semiconductor and metal nanocrystals, with an eye toward renewable energy technologies. If you had whispered to him, “What is Lee talking about, with these piperidines and heterocycles and such?” he would have explained that she was seeking to develop methods to synthesize drugs. He would have spoken of the “craftsmanship of synthetic chemistry” and the synthesis of molecules. “We build Lego sets,” he’d have said, “and it just so happens that the things we build have a function. If the world is better at synthesizing piperidines” — an organic compound found in black pepper and used in the synthesis of pharmaceuticals — “it may lead to some kind of a silver-bullet drug.”

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