Structures of fibrostatins, new inhibitors of prolyl hydroxylase

The structures of six inhibitors of prolyl hydroxylase, fibrostatins A, B, C, D, E and F produced by a strain of Streptomyces, were deduced to be 1, 2, 3, 4, 5 and 6, respectively, from chemical and spectroscopic evidence, especially from extensive 13C NMR studies including selective decoupling and low power selective decoupling experiments monitored by 13C-1H long-range couplings. These compounds are the first naturally occurring 2,6,7- or 3,6,7-tri-substituted or 2,3,6,7-tetra-substituted 5-hydroxy-1,4-naphthoquinone inhibitors possessing N-acetyl-L-cystein-S-yl moieties in the molecule.