Extension of hydrogen borrowing alkylation reactions for the total synthesis of (-)-γ-lycorane.

The total synthesis of (-)-γ-lycorane (10 steps) and synthesis of (±)-γ-lycorane (8 steps) was completed from cyclohexenone. A new two step hydrogen borrowing alkylation of an aziridinyl alcohol, coupled with a Ph* (Me5C6) deprotection/cyclisation procedure was developed for de novo formation of the fused 6,5 heterocyclic ring. This work is one of the first examples of hydrogen borrowing C-C bond formation being used as a key step in a total synthesis project.

Hydrogen-Borrowing Alkylation of 1,2-Amino Alcohols in the Synthesis of Enantioenriched γ-Aminobutyric Acids.

For the first time we have been able to employ enantiopure 1,2-amino alcohols derived from abundant amino acids in C-C bond-forming hydrogen-borrowing alkylation reactions. These reactions are facilitated by the use of the aryl ketone Ph*COMe. Racemisation of the amine stereocentre during alkylation can be prevented by the use of sub-stoichiometric base and protection of the nitrogen with a sterically hindered triphenylmethane (trityl) or benzyl group. The Ph* and trityl groups are readily cleaved in one pot to give γ-aminobutyric acid (GABA) products as their HCl salts without further purification. Both steps may be performed in sequence without isolation of the hydrogen-borrowing intermediate, removing the need for column chromatography.

Pyruvate Enolate Arylation and Alkylation: OBO Ester Protected Pyruvates as Useful Reagents in Organic Synthesis.

A protected pyruvate equivalent is described that allows arylation and arylation/alkylation reactions to be performed at the methyl group. Utilization of the OBO derivative of the pyruvate ester allowed the application of palladium catalyzed arylation reactions together with subsequent alkylation, under basic conditions. Moreover, the OBO protecting group could be easily removed in one step to provide access to a wide range of substituted pyruvate derivatives.