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 II 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 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)