I agree with many of the commenters around here that one of the most interesting and productive research frontiers in organic chemistry is where it runs into molecular biology. There are so many extraordinary tools that have been left lying around for us by billions of years of evolution; not picking them up and using them would be crazy.
Naturally enough, the first uses have been direct biological applications - mutating genes and their associated proteins (and then splicing them into living systems), techniques for purification, detection, and amplification of biomolecules. That's what these tools do, anyway, so applying them like this isn't much of a shift (which is one reason why so many of these have been able to work so well). But there's no reason not to push things further and find our own uses for the machinery.
Chemists have been working on that for quite a while. We look at enzymes and realize that these are the catalysts that we really want: fast, efficient, selective, working at room temperature under benign conditions. If you want molecular-level nanotechnology (not quite down to atomic!), then enzymes are it. The ways that they manipulate their substrates are the stuff of synthetic organic daydreams: hold down the damn molecule so it stays in one spot, activate that one functional group because you know right where it is and make it do what you want.
All sorts of synthetic enzyme attempts have been made over the years, with varying degrees of success. None of them have really approached the biological ideals, though. And in the "if you can't beat 'em, join 'em" category, a lot of work has gone into modifying existing enzymes to change their substrate preferences, product distributions, robustness, and turnover. This isn't easy. We know the broad features that make enzymes so powerful - or we think we do - but the real details of how they work, the whole story, often isn't easy to grasp. Right, that oxyanion hole is important: but just exactly how does it change the energy profile of the reaction? How much of the rate enhancement is due to entropic factors, and how much to enthalpic ones? Is lowering the energy of the transition state the key, or is it also a subtle raising of the energy of the starting material? What energetic prices are paid (and earned back) by the conformational changes the protein goes through during the catalytic cycle? There's a lot going on in there, and each enzyme avails itself of these effects differently. If it weren't such a versatile toolbox, the tools themselves wouldn't come out being so darn versatile.
There's a very interesting paper that's recently come on on this sort of thing, to which I'll devote a post by itself. But there are other biological frontiers beside enzymes. The machinery to manipulate DNA is exquisite stuff, for example. For quite a while, it wasn't clear how we organic chemists could hijack it for our own uses - after all, we don't spend a heck of a lot of time making DNA. But over the years, the technique of adding DNA segments onto small molecules and thus getting access to tools like PCR has been refined. There are a number of applications here, and I'd like to highlight some of those as well.
Then you have things like aptamers and other recognition technologies. These are, at heart, ways to try to recapitulate the selective binding that antibodies are capable of. All sorts of synthetic-antibody schemes have been proposed - from manipulating the native immune processes themselves, to making huge random libraries of biomolecules and zeroing in on the potent ones (aptamers) to completely synthetic polymer creations. There's a lot happening in this field, too, and the applications to analytical chemistry and purification technology are clear. This stuff starts to merge with the synthetic enzyme field after a point, too, and as we understand more about enzyme mechanisms that process looks to continue.
So those are three big areas where molecular biology and synthetic chemistry are starting to merge. There are others - I haven't even touched here on in vivo reactions and activity-based proteomics, for example, which is great stuff. I want to highlight these things in some upcoming posts, both because the research itself is fascinating, and because it helps to show that our field is nowhere near played out. There's a lot to know; there's a lot to do.