Absolute stereochemical assignment and fluorescence tuning of the small molecule tool, (-)-blebbistatin

(-)-Blebbistatin (1), a recently discovered small molecule inhibitor of the ATPase activity of non-muscle myosin 11 has been prepared from methyl 5-methylanthranilate (6) in three steps. This flexible synthetic route has also been used to prepare a nitro group-containing analogue 12 that has modified fluorescence properties and improved stability under microscope illumination. The key step in the synthesis of 1 and its analogues was the asymmetric hydroxylation of the quinolone intermediate 3 using the Davis oxaziridine methodology. The absolute stereochemistry of (-)-blebbistatin (1) was shown to be S by X-ray crystal structure analysis of a heavy atom (bromine) containing analogue 11, which was subsequently reduced and shown to be identical to 1. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).