Hi all! Although this news is actually over a week old (and things are still in progress), I have an announcement to make. As many of you may have noticed, my old webhosting sucked - my domain was unmemorable, and when you did find the site it was often down for some reason. Well, thanks to a generous gift from DrFreddy over at Synthetic Remarks I now have a new domain name, and some decent hosting to back it up! So, the reason for this post is twofold: firstly, to tell you all to update your bookmarks for I can now be found at brsmblog.com and secondly, to again thank DrFreddy for helping out a poor student - this is easily the nicest thing anyone's done for me all year!
By way of warning I should say that the database which powers the blog is still over at eristocracy.co.uk, which is slowing things down at the moment but it will hopefully be migrated soon, as are the schemes of posts written before last week because I can't seem to get the links to change to the new server. When these issues are resolved then everything should be much better. In the meantime, please be patient and expect things to be a little shakey for the next week or so while I work things out!
Note: In my opinion, it would be fairly ill advised to attempt any of these.
So, wax. According to wikipedia, a wax is just a plastic/malleable compound that melts slightly above room temperature to give a non viscous liquid. As this definition doesn't stipulate any chemical properties, there's a pretty large number of compounds which fall into this bracket, and so waxes from different sources can have very different chemical compositions. Wax from natural sources such as insects and animals tends to be composed of the esters of various fatty acids with long chain alcohols, whereas synthetic waxes tend to be simple mixtures of various long chain hydrocarbons. Earwax is different again. Regardless of its provenance, wax can be a pretty useful substance, with myriad uses around the lab. Here are the first five I can think of; no doubt there are others!
Update 26/11/11: Link to newly available SI now added!
Update 30/10/11: Also, Tot. Syn. now has a post on this.
Update 29/10/11: Covered in more colours over at synthetic nature. Check it out!
Carreira et al., Angew. Chem., 2011, Early View
Here's an interesting synthesis from a couple of weeks ago out of the Carreira lab - the first synthesis not only of daphmanidin E itself, but of any alkaloid of its family and skeleton. The daphmanidins constitute a recent addendum to the already fairly diverse class of alkaloids isolated from Daphniphyllaceae, with today's target only reported 5 years ago. Presumably, exciting features like "moderate vasorelaxant activity on rat aorta" and that well nested central bicyclo[2.2.2]octane ring make them tempting targets...
Anyone who's read some of the older chemical literature (or even recent papers by old school chemists) has probably noticed the 'black dot' notation used to depict stereochemistry at ring junctions, particularly by chemists in the US and Canada. Here's a recent example, so you'll know what I'm on about if you don't already.
I don't know how things are in the US, but at no point during my chemical education do I ever remember having this notation explained to me. I recall encountering it for the first time at the start of my PhD, asking around a bit, and then just working it out for myself. Turns out it's actually really simple - a black dot at a ring junction just means that the hydrogen there is on the β-face, i.e. above the plane of the paper. To this day I've never seen this explained in a textbook, and have wondered from time to time where the heck it came from. As named reactions become canonised, the references the seminal papers slowly disappear, and clearly the same thing has happened here, as with many other conventions and nomenclatures. However, not having a name for this notation I'd never been able to trace where it started. Until now.
Fukuyama et al. J. Am. Chem. Soc., 2011, ASAP
After what feels like a long dry spell in exciting total syntheses, Fukuyama and coworkers disclosed the first asymmetric synthesis of the natural product gelsemoxonine last week. Although not much is known about the biological activity of gelsemoxonine itself, the related natural products gelsedine and gelsenicine have been shown to exhibit potent cytotoxic activities and moreover, the densely functionalised oxabicyclo[3.2.2]nonane core with its azetidine and indolinone quaternary centres makes for an exciting synthetic target.
Sorry things have been so quiet around here the last couple of weeks - I've been a bit uninspired, the start of term has been a bit hectic, and my boss has finally noticed that I haven't really made any progress in the last six months. Hopefully more things soon as I wrestle my life back under control.
A few weeks ago, as the result of a conversation in the lab, I thought it might be interesting to pick a popular molecule (i.e. something of which there have been numerous syntheses), and see how much better we've gotten at making it over time. After a bit of thought I settled on strychnine, and in order to not waste an excessive amount of my life, only took syntheses which produced a single enantiomer of the natural product. So, first let us look at how the number of steps (in the longest linear sequence) has varied over the years.