Matthew J. Sharp

Total Synthesis of (±)-Gelsemine

A complex molecular reorganization (1-->2), a sequential anionic aza-Cope rearrangement and Mannich cyclization, and an unprecedented intramolecular Heck reaction of the tetrasubstituted double bond of a vinylogous carbamate are key steps in a new total synthesis of (+/-)-gelsemine (3). MOM=methoxymethyl, DBU=1,8-diazabicyclo[5.4.0]undec-7-ene.

An enyne cycloisomerization approach to the triple reuptake inhibitor GSK1360707F.

The triple reuptake inhibitor GSK1360707F was synthesized via an efficient and scalable route that features an enyne cycloisomerization reaction catalyzed by either Pt(II) or Au(I). Key aspects of this work such as the choice of the nitrogen protecting group and initial enantioselectivity studies are discussed.

Asymmetric Synthesis of an N-Acylpyrrolidine for Inhibition of HCV Polymerase

A practical asymmetric synthesis of a highly substituted N-acylpyrrolidine on multi-kilogram scale is described. The key step in the construction of the three stereocenters is a [3+2] cycloaddition of methyl acrylate and an imino ester prepared from l-leucine t-butyl ester hydrochloride and 2-thiazolecarboxaldehyde. The cycloaddition features novel asymmetric catalysis via a complex of silver acetate and a cinchona alkaloid, particularly hydroquinine, with complete diastereomeric control and up to 87% enantiomeric control. The alkaloid serves as a ligand as well as a base for the formation of the azomethine ylide or 1,3-dipole. Experiments have shown that the hydroxyl group of hydroquinine is a critical element for the enantioselectivities observed. The cycloaddition methodology is also applicable to methylvinyl ketone, providing access to either alpha- or beta-epimers of 4-acetylpyrrolidine depending on the reaction conditions utilized. The synthesis also highlights an efficient N-acylation, selective O- versus N-methylation, and a unique ester reduction with NaBH4-MeOH catalyzed by NaB(OAc)3H that not only achieves excellent chemoselectivity but also avoids formation of the undesired but thermodynamically favored epimer. The highly functionalized target is synthesized in seven linear steps from l-leucine t-butyl ester hydrochloride with all three isolated intermediates being highly crystalline.

Enantioselective total synthesis of the pumiliotoxin A alkaloids via reductive iminium ion-alkyne cyclizations. Total synthesis of (+)-pumiliotoxin A

Abstract A highly practical new route for the enantioselective synthesis of the pumiliotoxin A alkaloids in which the title reaction is a key step is disclosed.

TOTALSYNTHESE VON ()-GELSEMIN

Eine komplexemolekulareReorganisation (1→2), eine Sequenz aus Aza-Cope-Umlagerung und Mannich-Cyclisierung und eine neuartige intramolekulare Heck-Reaktion der tetrasubstituierten Doppelbindung eines vinylogen Carbamats sind die Schlusselschritte einer neuen Totalsynthese von (±)-Gelsemin 3. MOM=Methoxymethyl, DBU=1,8-Diazabicyclo[5.4.0]undec-7-en.

Biological and Structural Characterization of Rotamers of C-C Chemokine Receptor Type 5 (CCR5) Inhibitor GSK214096.

We recently reported the discovery of preclinical CCR5 inhibitor GSK214096, 1 (J. Med. Chem. 2011, 54, 756). Detailed characterization of 1 revealed that it exists as a mixture of four separable atropisomers A-D. The two slow-interconverting pairs of rotamers A + B and C + D were separated and further characterized. HIV and CCR5-mediated chemotaxis data strongly suggest that the antiviral potency of 1 is due to rotamers A + B and not C + D. Furthermore, integrated UV, vibrational circular dichroism VCD and computational approach allowed to determine the M chirality in C + D (and P chirality in A + B). These findings imply additional avenues to be pursued toward new CCR5 antagonists.