ioc wireup.cs

public static class StructuremapMvc
{
	public static void Start()
	{
		var container = IoC.Initialize();
		GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerActivator), new StructureMapHttpControllerActivator(container));
	}
}

StructureMapHttpControllerActivator.cs

public class StructureMapHttpControllerActivator : IHttpControllerActivator
{
  private readonly IContainer _container;

  public StructureMapHttpControllerActivator(IContainer container)
  {
    _container = container;
  }

  public IHttpController Create(
          HttpRequestMessage request,
          HttpControllerDescriptor controllerDescriptor,
          Type controllerType)
  {
    var nestedContainer = _container.GetNestedContainer();
    nestedContainer.Inject(typeof(HttpRequestMessage), request);

    request.RegisterForDispose(nestedContainer);
    return (IHttpController)nestedContainer.GetInstance(controllerType); 
  }
}