Dual Platinum and Pyrrolidine Catalysis in the Direct Alkylation of Allylic Alcohols: Selective Synthesis of Monoallylation Products

Bioconjugation with Thiols by Benzylic Substitution

A benzylic substitution of 3-indolyl(hydroxyl)acetate derivatives with thiols proceeded specifically in the presence of amino, carboxy, and phosphate groups in weakly acidic aqueous solutions under nearly physiological condition, while no reaction occurred at pH over 7. Kinetic studies revealed that the reaction followed second-order kinetics (first-order in the reactant and first-order in thiol) in contrast with the S_N 1 mechanism of common benzylic substitution of alcohols. The utility of the present method for functionalization of biomacromolecules was demonstrated using several model proteins, such as lysozyme, insulin, trypsin, and serum albumin. The catalytic bioactivity of lysozyme in lysis of Micrococcus lysodeikticus cells was completely retained after the modification.

A Mixed-Ligand Chiral Rhodium(II) Catalyst Enables the Enantioselective Total Synthesis of Piperarborenine B

A novel, mixed-ligand chiral rhodium(II) catalyst, Rh2(S-NTTL)3(dCPA), has enabled the first enantioselective total synthesis of the natural product piperarborenine B. A crystal structure of Rh2(S-NTTL)3(dCPA) reveals a "chiral crown" conformation with a bulky dicyclohexylphenyl acetate ligand and three N-naphthalimido groups oriented on the same face of the catalyst. The natural product was prepared on large scale using rhodium-catalyzed bicyclobutanation/ copper-catalyzed homoconjugate addition chemistry in the key step. The route proceeds in ten steps with an 8% overall yield and 92% ee.

Iron-Catalyzed Allylic Amination Directly from Allylic Alcohols

Allylic amination, directly from alcohols, has been demonstrated without any Lewis acid activators using an efficient and regiospecific molecular iron catalyst. Various amines and alcohols were employed and the reaction proceeded through the oxidation/reduction (redox) pathway. A direct one-step synthesis of common drugs, such as cinnarizine and nafetifine, was exhibited from cinnamyl alcohol that produced water as side product.

Asymmetric Allylic Alkylation of β-Ketoesters with Allylic Alcohols by a Nickel/Diphosphine Catalyst

Asymmetric allylic alkylation of β-ketoesters with allylic alcohols catalyzed by [Ni(cod)2]/(S)-H8-BINAP was found to be a superior synthetic protocol for constructing quaternary chiral centers at the α-position of β-ketoesters. The reaction proceeded in high yield and with high enantioselectivity using various β-ketoesters and allylic alcohols, without any additional activators. The versatility of this methodology for accessing useful and enantioenriched products was demonstrated.