Chemoselective Acylation of Nucleosides.

Acylated nucleoside analogues play an important role in medicinal chemistry and are extremely useful precursors to various other nucleoside analogues. However, chemoselective acylation of nucleosides usually requires several protection and deprotection steps due to the competing nucleophilicity of hydroxy and amino groups. In contrast, direct protecting-group-free chemoselective acylation of nucleosides is a preferred strategy due to lower cost and fewer overall synthetic steps. Herein, a simple and efficient chemoselective acylation of nucleosides and nucleotides under mild reaction conditions, giving either O- or N-acylated products respectively with excellent chemoselectivity is reported.

Catalytic asymmetric and stereodivergent oligonucleotide synthesis.

We report the catalytic stereocontrolled synthesis of dinucleotides. We have demonstrated, for the first time to our knowledge, that chiral phosphoric acid (CPA) catalysts control the formation of stereogenic phosphorous centers during phosphoramidite transfer. Unprecedented levels of diastereodivergence have also been demonstrated, enabling access to either phosphite diastereomer. Two different CPA scaffolds have proven to be essential for achieving stereodivergence: peptide-embedded phosphothreonine-derived CPAs, which reinforce and amplify the inherent substrate preference, and C2-symmetric BINOL-derived CPAs, which completely overturn this stereochemical preference. The presently reported catalytic method does not require stoichiometric activators or chiral auxiliaries and enables asymmetric catalysis with readily available phosphoramidites. The method was applied to the stereocontrolled synthesis of diastereomeric dinucleotides as well as cyclic dinucleotides, which are of broad interest in immuno-oncology as agonists of the stimulator of interferon genes (STING) pathway.

Catalytic Asymmetric Synthesis of α-Arylpyrrolidines and Benzo-fused Nitrogen Heterocycles.

Herein, we report a practical two-step synthetic route to α-arylpyrrolidines through Suzuki-Miyaura cross-coupling and enantioselective copper-catalyzed intramolecular hydroamination reactions. The excellent stereoselectivity and broad scope for the transformation of substrates with pharmaceutically relevant heteroarenes render this method a practical and versatile approach for pyrrolidine synthesis. Additionally, this intramolecular hydroamination strategy facilitates the asymmetric synthesis of tetrahydroisoquinolines and medium-ring dibenzo-fused nitrogen heterocycles.

CuH-Catalyzed Asymmetric Hydroamidation of Vinylarenes.

A CuH-catalyzed enantioselective hydroamidation reaction of vinylarenes has been developed using readily accessible 1,4,2-dioxazol-5-ones as electrophilic amidating reagents. This method provides a straightforward and efficient approach to synthesize chiral amides in good yields with high levels of enantiopurity under mild conditions. Moreover, this transformation tolerates substrates bearing a broad range of functional groups.

Stereoselective Organocatalyzed Synthesis of α-Fluorinated ß-Amino Thioesters and Their Application in Peptide Synthesis.

α-Fluorinated ß-amino thioesters were obtained in high yields and stereoselectivities by organocatalyzed addition reactions of α-fluorinated monothiomalonates (F-MTMs) to N-Cbz- and N-Boc-protected imines. The transformation requires catalyst loadings of only 1 mol % and proceeds under mild reaction conditions. The obtained addition products were readily used for coupling-reagent-free peptide synthesis in solution and on solid phase. The α-fluoro-ß-(carb)amido moiety showed distinct conformational preferences, as determined by crystal structure and NMR spectroscopic analysis.

Stereoselective Organocatalytic Synthesis of Oxindoles with Adjacent Tetrasubstituted Stereocenters.

Oxindoles with adjacent tetrasubstituted stereocenters were obtained in high yields and stereoselectivities by organocatalyzed conjugate addition reactions of monothiomalonates (MTMs) to isatin-derived N-Cbz ketimines. The method requires only a low catalyst loading (2 mol %) and proceeds under mild reaction conditions. Both enantiomers are accessible in good yields and excellent stereoselectivities by using either Takemoto's catalyst or a cinchona alkaloid derivative. The synthetic methodology allowed establishment of a straightforward route to derivatives of the gastrin/cholecystokinin-B receptor antagonist AG-041R.

Organocatalytic route to dihydrocoumarins and dihydroquinolinones in all stereochemical configurations.

A straightforward stereodivergent route to dihydrocoumarins and dihydroquinolinones based on cinchona alkaloid catalyzed addition reactions of monothiomalonates (MTMs) to functionalized nitroolefins followed by deprotection and chemoselective cyclization has been developed. The synthesis proceeds under mild conditions and yields heterocycles with adjacent quaternary and tertiary stereogenic centers in very high yields and stereoselectivities. Moreover, full control over the relative and absolute configuration is achieved by the use of (pseudo)enantiomeric catalysts and the difference in reactivity of thioester versus oxoester moieties.