Organic Colloquium Presents The 2018 Christopher S. Foote Lecture

Professor Eric Block Carla Rizzo Delray Distinguished Professor of Department of Chemistry, University at Albany, State University of New York Visiting Scholar, Department of Chemistry, University of California, Los Angeles

Fifty Years of Smelling Sulfur: From the Chemistry of to the Molecular Basis for Olfaction

Abstract. Smell is one of five senses through which we perceive the world. By one estimate, humans can sense more than one trillion olfactory stimuli. My talk will focus on strong-smelling sulfur-containing odorants, whose chemistry I have been studying for more than 50 years. I have particularly specialized in sulfur compounds from garlic, and related species (“Allium chemistry”). My Allium research began with papers in the 1970’s in collaboration with University of Missouri–St. Louis colleague R.W. Murray showing that disulfides could be oxidized with singlet oxygen sources giving thiosulfinates, RS(O)SR, key Allium flavor compounds.

PhO O 1 PhO P O or O2 PhO O RSSR RS(O)SR

Humans and animals have an exquisitely sensitive toward low-valent, volatile sulfur compounds. In 1887, Emil Fischer wrote that concentrations of ethanethiol as low as 0.05 ppb are “clearly perceptible to the sense of smell”. Chiral 3-methyl-3-sulfanylhexan-1-ol, in onions and in armpit odor, can be perceived at levels as low as

0.000001 ppb. In 2005, with colleagues, we identified (methylthio)methanethiol (MeSCH2SH; MTMT) as a garlic- smelling social-signaling compound found in mouse urine. We then identified the mouse odorant receptor (OR), MOR244-3, responding robustly to MTMT, and the human receptor OR2T11, responding to 2-methyl-2-propanethiol, the odorant in natural gas, 2-propenethiol from garlic, and other low-molecular-weight . Both receptors require Cu as cofactor.

Thursday, January 18, 2018 5:00 PM Molecular Science 3440 For further information, contact Nikki Erinakis at [email protected]