A rapid and convenient synthesis of β-proline

Synthesis of pyrrolidine-3-carboxylic acid derivatives via asymmetric Michael addition reactions of carboxylate-substituted enones

An enantioselective Michael addition reaction system was developed. Using the reaction system, 5-methylpyrrolidine-3-carboxylic acid was synthesized in two steps.

Synthesis and determination of absolute configuration of a non-peptidic αvβ6 integrin antagonist for the treatment of idiopathic pulmonary fibrosis

Integrin inhibitor (cell adhesion assays) pIC₅₀ α_vβ₆ = 8.4, α_vβ₃ = 6.0, α_vβ₅ = 5.9 and α_vβ₈ = 7.7.

Using heteroaryl-lithium reagents as hydroxycarbonyl anion equivalents in conjugate addition reactions with (S,S)-(+)-pseudoephedrine as chiral auxiliary; enantioselective synthesis of 3-substituted pyrrolidines

We have developed an efficient protocol for carrying out the stereocontrolled formal conjugate addition of hydroxycarbonyl anion equivalents to α,β-unsaturated carboxylic acid derivatives using (S,S)-(+)-pseudoephedrine as chiral auxiliary, making use of the synthetic equivalence between the heteroaryl moieties and the carboxylate group. This protocol has been applied as key step in the enantioselective synthesis of 3-substituted pyrrolidines in which, after removing the chiral auxiliary, the heteroaryl moiety is converted into a carboxylate group followed by reduction and double nucleophilic displacement. Alternatively, the access to the same type of heterocyclic scaffold but with opposite absolute configuration has also been accomplished by making use of the regio- and diastereoselective conjugate addition of organolithium reagents to α,β,γ,δ-unsaturated amides derived from the same chiral auxiliary followed by chiral auxiliary removal, ozonolysis, and reductive amination/intramolecular nucleophilic displacement sequence.

A stereoselective cyclization strategy for the preparation of γ-lactams and their use in the synthesis of α-methyl-β-proline

A straightforward stereoselective and enantiodivergent cyclization strategy for the construction of γ-lactams is described. The cyclization strategy makes use of chiral malonic esters prepared from enantiomerically enriched monoesters of disubstituted malonic acid. The cyclization occurs with the selective displacement of a substituted benzyl alcohol as the leaving group. A Hammett study illustrates that the cyclization is under electronic control. The resulting γ-lactam can be readily converted into a novel proline analogue.

Introduction of C(5/6) side chains onto 2-azabicyclo[2.1.1]hexanes via a 6-anti-bromo-5-anti-hydroxy derivative

Oxidation of the title bromoalcohol provided the strained ketone, 5-bromo-6-oxo-2-azabicyclo[2.1.1]hexane. Additions of nucleophiles to either this or the debrominated ketone have been used to introduce 5(6)-syn-alkyl and aryl groups, 5(6)-alkylidene linkages, and 5(6)-anti-alkyl and acyl substituents. Facial selectivity is for additions to the 6-bromo-5-ketone and 5-alkylidene azabicycles to occur from the face syn to the nitrogen atom. The bromine atom of the title alcohol has also been replaced by a 6-anti-(1-hydroxyethyl) substituent using a directed radical addition process. The stereoselective functionalization reactions expand the range of available methano-bridged pyrrolidines.