It also seems plausible to consider that the enhanced H-bonding behavior derived from the Lewis basic character of the amides plays a directing role in inducing the high site-selectivity for C3-H oxidation. The beneficial effect of this directing role is complementary to the non-covalent interactions established with the bulky trialkyl silyl groups, which synergistically contribute to the destabilization of TS minor . This effect is well-collected by the SterimolC3-R term of the catalysts model, which may be important for enantioinduction in substrates lacking a carbonyl moiety at C1 such as S3 and S4.