The copper-catalyzed asymmetric conjugate addition of organometallic reagents is today one of the most powerful and versatile tools for enantioselective C-C bond formation. Following the recent progresses in the field of alkenylalanes chemistry, the first objective of this thesis work was to broaden the use of these nucleophiles in asymmetric 1,4-additions. In this context, a series of alkenyl groups have been successfully introduced to a challenging class of Michael acceptors, the α,β-unsaturated lactams, affording valuable building blocks for the preparation of optically active N-heterocycles. The second objective of this work was to develop an efficient approach towards the synthesis of Riccardiphenol B, a sesquiterpene derivative isolated from a Japanese collection of the liverwort Riccardia crassa, by using two methodologies developed in our group. We managed to complete the total synthesis of this natural product, which was prepared in 10 steps with an overall yield of 2.7%.