Wednesday, May 16, 2007

Chimie

Please pardon my lack of posts. I'm traveling in France for a couple of weeks and haven't had a chance to write anything. I visited l'École Nationale Supérieure today. I was able to see original research samples from Louis Pasteur. What a treat!



Tuesday, May 8, 2007

Odeur d'Asperge


Yes, it is asparagus season. I love this vegetable. Raw straight out of the garden, steamed with white wine and garlic, coated with olive oil and roasted on the grill, I can't get enough of it! Of course, for some of us that means plenty of malodorous urinary discharge. Yes, I'm talking about the infamous Asparagus Pee! The culprit - Asparagusic Acid. Derived from valine, this acid is unique to asparagus and appears to be the metabolic precursor to a number of odiferous sulfur-containing compounds. In it's pure form, this colorless solid melts around 76 °C. For those with the enzyme to break it down (~40% of the population) the results appear in the urine usually within 15 minutes of ingestion. Interestingly, not everyone has the ability to smell the satisfying stench, thus complicating studies to determine why some have smelly piss and others do not. I am one of the lucky ones who can both produce copious quantities of metabolites such as methyl thioacrylate (among others) and delight in its pleasing perfume. For those of you deprived of this evolutionary gift, I have sympathy, as you will never truly enjoy the full experience of asparagus season.


(edited 5/8/07, 5:28 pm to fix structures)

Wednesday, May 2, 2007

Your Road to a PhD

I'd like to call out some of the lurkers who read my blog to come forward and make some comments. I'm curious to find out what influences a student's decision for choice of graduate school in chemistry. So, if you have your PhD, are in a PhD program now, or going to join a PhD program soon, please tell me what was important for your choice of school. Was it location? Science? Stipend? What? Did family issues change your decision? Would you only look at schools on the coasts, or did you look across the middle of the country too? How influential were your undergraduate mentors? What about international studies? This would apply to those from the US going abroad as well as those from outside the US coming to America. And finally, what sources did you use to find graduate programs? Do you put any stock in the web sites that list rankings of graduate programs?

Tuesday, May 1, 2007

A Rhodium Thing

Ever since my first encounter with aldehyde C-H insertion by rhodium, I have been intrigued by the possibilities of the acylorganometallic intermediates. In Org. Lett. a nice formal [4+2] cycloaddition appeared utilizing ortho-vinyl benazaldehydes and olefins or alkynes. The reaction proceeds via C-H insertion to form an acylrhodium followed by a migratory insertion to produce a rhodacylopentene. This reacts with an alkene to form the product shown. Chiral ferrocenyl phosphine ligands afforded at least modest level of enationselectivity. If alkynes were utilized, napthol products were produced. Although most yields and selectivities were modest, it is an interesting transformation. It seems to be limited in scope. Without the arene ring cyclization did not take place. Instead the acylrhodium simply reacts with the olefin in a reductive Heck-type process to afford an acyclic ketone.

Ken Tanaka, Daiki Hojo, Takeaki Shoji, Yuji Hagiwara, and Masao Hirano, DOI: 10.1021/ol0704587