2H-1,2-Oxazine-6-carboxylic acid, tetrahydro-2-[[(6R)-tetrahydro-2-[[(6R)-tetrahydro-2-[[(6R)-tetrahydro-2 H-1,2-oxazin-6-yl]carbonyl]-2H-1,2-oxazin-6-yl]carbonyl]-2H-1,2-oxazin- 6-yl]carbonyl]-, (