As much as I’ve enjoyed my forays into analytical and flavour chemistry, yesterday afternoon I had a relapse and attended the Arthur C. Cope session on organic chemistry in the cathedral-sized ballroom. Actually, the cathedral analogy doesn’t seem a bad one, as sometimes it does feel as if there’s a certain amount of worshipping going on.

I really enjoyed this session because it had an ecelectic mix of topics. Highlights for me included Kenneth Shea‘s talk on how to build polyethylene molecules from single-carbon units, in a living polymerization reaction involving ylides and diazoalkanes. In this way, he’s made some unusual polymers – such as chains with high steric congestion that can’t be prepared using traditional methods for polyolefin preparation.

I also liked Leonard MacGillivray’s presentation on solid-phase organic reactions. He co-crystallizes pairs of organic compounds to form lattices in which hydrogen-bonding aligns the molecules in a perfect orientation for reaction – specifically, photodimerization reactions between alkenes to form cyclobutanes. Because the lattice holds the molecules in very specific orientations, the stereochemistry of the process is precisely controlled.

But my favourites were Dave Macmillan and Andre Charette. Charette described his work on the preparation of chiral amines by adding organozinc reagents to N-phosphinoylimines. Now I’ve always been a bit dubious about dialkylzinc compounds, because they’re a pain to make. But Charette has thought of this, and has developed a relatively simple way to make them from zinc methoxide – so top marks for thinking of the practicalities.

MacMillan discussed his work on SOMO-activation reactions using organocatalysis. I liked the way that he gave much of the credit for this idea to his co-worker, Teresa Beeson. His group are currently developing new reactions using SOMO-activation, so expect to see enantioselective alpha-halogenation of aldehydes, vinylation reactions, and the enentioselective alkylation of cyclic ketones (which apparently requires a completely different catalyst to the one currently published).

All in all it was a top session. The only down-side was the way that people in the audience would get up and leave as soon as the speaker they were interested in had finished. I know that people have to focus on lectures in their own fields to get the most out of these meetings, but if they’d stuck around for the whole session I think they’d have found the variety of topics refreshing and stimulating.

Andy

Andrew Mitchinson (Associate editor, Nature)

It ain’t easy working in the field of ancient DNA, as Alan Cooper of the University of Adelaide will tell you. His lab works on cool specimens such as Neanderthal teeth, bison bones, and moa poo, trying to extract signs of long-gone life.

But getting DNA out of old specimens is subject to many whims of fate, Cooper told the meeting in a plenary lecture today. One time his team tried to run sequences on a Viking skull from Greenland – and got 23 sequences from 23 separate individuals. “Probably 23 archaeologists,” Cooper jokes.

Technicians in ancient DNA laboratories have to take special care not to contaminate the material they’re working with. They suit up in clean suits, wear surgical gloves that they change regularly, and work in rooms with negative air pressure to blow contaminants out. Lab equipment has to be sterilized with ultraviolet radiation because it can be contaminated with mouse droppings. Visitors have to wear visors because the fluttering of eyelashes can spread DNA everywhere.

But if it’s done right, ancient DNA can reveal a lot about long-lost worlds – like the fact that different-sized moas can be just different sexes and not different species, or that bison in North America may have been starting to crash before human hunters ever showed up on the plains.

Findings like that are probably worth all the tidying up around the lab.