Ru(II)-catalyzed cascade reactions in stereocontrolled construction of rigid as-indacene-bridged bis(alpha-amino acid) derivatives

The key construction in the preparation of as-indacene-bridged bis(alpha-amino acid) derivatives was effected by a Ru(II)-catalyzed RCM cascade reaction of appropriately substituted triynes. The latter were available after stepwise and stereocontrolled alkynylations of (2R)-2,5-dihydro-2-isopropyl-3,6-dimethoxypyrazine as chiral auxiliary. The regio- and stereochemical transformations have been verified by a single-crystal X-ray analysis.