A stereoselective approach for the total synthesis of (−)-tadanalactam from acetonide-d-glucose

A Lewis Acid-Controlled Enantiodivergent Epoxidation of Aldehydes

Two epoxidation catalysts, one of which consists of two VANOL ligands and an aluminum and the other that consists of two VANOL ligands and a boron, were compared. Both catalysts are highly effective in the catalytic asymmetric epoxidation of a variety of aromatic and aliphatic aldehydes with diazoacetamides, giving high yields and excellent asymmetric inductions. The aluminum catalyst is effective at 0 °C and the boron catalyst at -40 °C. Although both the aluminum and boron catalysts of (R)-VANOL give very high asymmetric inductions (up to 99% ee), they give opposite enantiomers of the epoxide. The mechanism, rate- and enantioselectivity-determining step, and origin of enantiodivergence are evaluated using density functional theory calculations.

Transition-Metal-Free Functionalization of Saturated and Unsaturated Amines to Bioactive Alkaloids Mediated by Sodium Chlorite

New approaches to the synthesis of alkaloids through the straightforward functionalization of C(sp3)–H and C(sp2)=C(sp2) bonds of simple five- and six-membered-ring N-heterocycles are highlighted. The direct functionalization of pre-existing N-heterocycles to advanced alkaloids intermediates is a chemical operation that commonly requires the intervention of transition or precious metals. Regardless the inherent unwanted waste production, the high economical cost of many transition-metal catalysts limits their use globally. Here, we account our efforts directed toward the synthesis of bioactive alkaloids under an economic and ecological fashion by using NaClO2 as the key activating or oxidizing reagent that substitutes the use of transition-metal catalysts. While undesired metal wastes are collected during the extraction process of a transition-metal-catalyzed reaction, innocuous NaCl is the commonly product waste when NaClO2 is employed in our chemical transformations. Beginning with the synthesis of 2,3-epoxyamides from allyl amines, we concluded with the functionalization of multiple and remote C(sp3)–H and C(sp3)–C(sp3) bonds in piperidine rings that enabled the preparation of important bioactive alkaloids. For the latter functionalization, a precise amount of co-oxidant reagent (NaOCl) and radical 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) were needed.

1 Introduction

2 Direct Chemical Method for Preparing 2,3-Epoxyamides

3 Dual C(sp3)–H Oxidation of Cyclic Amines to 3‑Alkoxyamine Lac­tams

4 Electrochemical Deamination of 3-Alkoxyamine Lactams

5 Direct C–H Oxidation of Piperazines and Morpholines to 2,3-Diketopiperazines and 3-Morpholinones, Respectively

6 Transition-Metal-Free Triple C–H Oxidation

7 Deconstructive Lactamization of Piperidines

8 Conclusion

Iron-Catalyzed Radical Cleavage/C-C Bond Formation of Acetal-Derived Alkylsilyl Peroxides

A novel radical-based approach for the iron-catalyzed selective cleavage of acetal-derived alkylsilyl peroxides, followed by the formation of a carbon-carbon bond is reported. The reaction proceeds under mild reaction conditions and exhibits a broad substrate scope with respect to the acetal moiety and the carbon electrophile. Mechanistic studies suggest that the present reaction proceeds through a free-radical process involving carbon radicals generated by the homolytic cleavage of a carbon-carbon bond within the acetal moiety. A synthetic application of this method to sugar-derived alkylsilyl peroxides is also described.

The direct and highly diastereoselective synthesis of 3,4-epoxy-2-piperidones. Application to the total synthesis and absolute configurational assignment of 3α,4α-epoxy-5β-pipermethystine

The substrate-controlled asymmetric total synthesis and absolute configurational assignment of biologically active 3α,4α-epoxy-5β-pipermethystine is reported.

Synthesis of the Enantiomers of Tedanalactam and the First Total Synthesis and Configurational Assignment of (+)-Piplaroxide

Highlighting the recently established methodology for the direct synthesis of glycidic amides from tertiary allyl amines, the synthesis of the enantiomers of tedanalactam were completed in two steps from the corresponding chiral dihydropiperidine. Additionally, the (+)- and (-)-enantiomers of piplaroxide were obtained from their respective tedanalactam precursor, and the absolute configuration of the naturally occurring (+)-piplaroxide was determined. The present approach represents not only the shortest synthesis of (-)-tedanalactam but also the first total synthesis of (+)-piplaroxide, a repellent against the leafcutter ant Atta cephalotes.