The Cu-catalyzed asymmetric conjugate hydroboration reaction of β-substituted α-dehydroamino acid derivatives has been established, affording enantioenriched syn- and anti-β-boronate-α-amino acid derivatives with excellent combined yields (83-99%, dr ≈ 1:1) and excellent enantioselectivities (92-98% ee). The hydroboration products were expediently converted into valuable β-hydroxy-α-amino acid derivatives, which were widely used in the preparation of chiral drugs and bioactive molecules.
The convenient preparation of N2-unprotected
five-membered cyclic
guanidines was achieved through a cascade [3 + 2] cycloaddition between
organo-cyanamides and α-haloamides under mild conditions in
good to excellent yields (up to 99%). The corresponding cyclic guanidines
could be easily transformed into hydantoins via hydrolysis.
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