Lushi Tan

A Novel, Highly Enantioselective Ketone Alkynylation Reaction Mediated by Chiral Zinc Aminoalkoxides

Kilogram-scale synthesis of the HIV reverse transcriptase inhibitor efavirenz was achieved by means of a highly enantioselective alkynylation of prochiral ketones 1 with alkynyllithium or alkynylmagnesium reagents in the presence of chiral zinc aminoalkoxides as mediators. With the achiral auxiliary 2,2,2-trifluoroethanol (R3 =CF3 CH2 ), the efavirenz precursor 2 (R1 =H, R2 =cyclopropyl) was obtained with an ee of 99.2%.

Rhodium‐Catalyzed Regioselective C7‐Functionalization of N‐Pivaloylindoles

An efficient rhodium-catalyzed method for direct C-H functionalization at the C7 position of a wide range of indoles has been developed. Good to excellent yields of alkenylation products were observed with acrylates, styrenes, and vinyl phenyl sulfones, whereas the saturated alkylation products were obtained in good yield with α,β-unsaturated ketones. Both the N-pivaloyl directing group and the rhodium catalyst proved to be crucial for high regioselectivity and conversion.

Dynamic Kinetic Resolution: Asymmetric Transfer Hydrogenation of α-Alkyl-Substituted β-Ketoamides

Dynamic kinetic resolution (deracemization) of various alpha-alkyl-substituted beta-ketoamides 1 via asymmetric transfer hydrogenation proceeded efficiently to give the corresponding syn-beta-hydroxy amides 3 in high diastereo- and enantioselectivities. Specifically, subjection of 1 to HCO(2)H and Et(3)N in the presence of 0.5-1 mol % of pentafluorobenzenesulfonyl-DPEN-Ru catalyst 2b at 30-40 degrees C in either PhCH(3) or CH(2)Cl(2) generated the syn-hydroxy product 3 selectively in 15-33:1 dr, 93-97% ee, and 75-88% isolated yields.

Eine neue, hochenantioselektive Alkinylierung von Ketonen, die durch chirale Zinkaminoalkoxide gesteuert wird

Im Kilogramm-Masstab gelang die Synthese von Efavirenz, einem zugelassenen Hemmstoff der Reversen Transkriptase des HI-Virus. Dabei wurde die hochenantioselektive Alkinylierung der prochiralen Ketone 1 mit Alkinyllithium- oder Alkinylmagnesiumreagentien durch chirale Zinkaminoalkoxide unterstutzt. Mit 2,2,2-Trifluorethanol als achiralem Hilfsstoff (R3 = CF3CH2) wurde die Efavirenz-Vorstufe 2 (R1 = H, R2 = Cyclopropyl) in 99.2 % ee erhalten.

Practical synthesis of a highly functionalized thiazole ketone

Abstract Compound 1 is a uniquely substituted ketone prepared via addition of a thiazole anion to an aromatic nitrile in good overall yield. An exploration into the generality of the addition of thiazole anions to nitriles allowed us to make a variety of thiazole ketones in good to excellent yields. The non-odorous thiolate-mediated demethylation reaction used in the synthesis of 1 is also presented.

Catalytic enantioselective hydrogenation of N-alkoxycarbonyl hydrazones: a practical synthesis of chiral hydrazines.

An enantioselective hydrogenation of hydrazones catalyzed by Rh complexes (Rh-Josiphos or Rh-Taniaphos) has been developed. The protocol can be applied to hydrazones with three different protective groups (Boc, Cbz, and methoxycarbonyl), allowing for selective deprotection and further elaboration of the hydrazine products in the presence of other functional groups.

Practical enantioselective synthesis of a COX-2 specific inhibitor

Abstract Two synthetic strategies to the COX-2 specific inhibitor 1 have been described that allowed its preparation in large quantities in 79% overall yield from (S)-2-hydroxy-2-methylbutyric acid. These studies have led to the identification of an efficient resolution of (±)-2-hydroxy-2-methylbutyric acid and a novel thionyl chloride aided formation of amide 11 from acid 6 .

Synthesis of Bis-Macrocyclic HCV Protease Inhibitor MK-6325 via Intramolecular sp2–sp3 Suzuki–Miyaura Coupling and Ring Closing Metathesis

A practical asymmetric synthesis of the complex fused bis-macrocyclic HCV protease inhibitor MK-6325 (1) is described. Through the combination of a high yielding and low catalyst loading ring-closing metathesis (RCM) to forge the 15-membered macrocycle with an intramolecular sp(2)-sp(3) Suzuki-Miyaura cross-coupling to append the 18-membered macrocycle, multikilogram access to the unique and challenging architecture of MK-6325 (1) has been achieved.

Asymmetric Formal Synthesis of the Long-acting DPP-4 Inhibitor Omarigliptin

A highly efficient asymmetric synthesis of the key tetrahydropyranol intermediate of DPP-4 inhibitor omarigliptin (1) is described. The successful development of a protecting-group- and precious-metal-free synthesis was achieved via the discovery of a practical asymmetric Henry reaction and the application of a one-pot nitro-Michael-lactolization-dehydration through-process. Other features of the synthesis include a highly efficient MsCl-mediated dehydration and a crystallization-induced dynamic resolution for exceptional ee and dr upgrade. The synthesis of this complex intermediate utilizes simple starting materials and proceeds in four linear steps.

A Next Generation Synthesis of BACE1 Inhibitor Verubecestat (MK-8931)

The development of a commercial manufacturing route to verubecestat (MK-8931) is described, highlights of which include the application of a continuous processing step to outcompete fast proton transfer in a Mannich-type ketimine addition, a copper-catalyzed amidation reaction, and an optimized guanidinylation procedure to form the key iminothiadiazine dioxide core.