Total Chemical Synthesis of the SARS-CoV-2 Spike Receptor-Binding Domain.

SARS-CoV-2 and its global spread have created an unprecedented public health crisis. The spike protein of SARS-CoV-2 has gained significant attention due to its crucial role in viral entry into host cells and its potential as both a prophylactic and a target for therapeutic interventions. Herein, we report the first successful total synthesis of the SARS-CoV-2 spike protein receptor binding domain (RBD), highlighting the key challenges and the strategies employed to overcome them. Appropriate utilization of advanced solid phase peptide synthesis and cutting-edge native chemical ligation methods have facilitated the synthesis of this moderately large protein molecule. We discuss the problems encountered during the chemical synthesis and approaches taken to optimize the yield and the purity of the synthetic protein molecule. Furthermore, we demonstrate that the chemically synthesized homogeneous spike RBD efficiently binds to the known mini-protein binder LCB1. The successful chemical synthesis of the spike RBD presented here can be utilized to gain valuable insights into SARS-CoV-2 spike RBD biology, advancing our understanding and aiding the development of intervention strategies to combat future coronavirus outbreaks. The modular synthetic approach described in this study can be effectively implemented in the synthesis of other mutated variants or enantiomer of the spike RBD for mirror-image drug discovery.

Rhodium(III)-Catalyzed Diastereoselective Ring-Opening of 7-Azabenzonorbornadienes with Aromatic Ketoximes: Synthesis of Benzophenanthridine Derivatives.

A rhodium(III)-catalyzed redox-neutral ring-opening of 7-azabenzonorbornadienes with aromatic ketoximes giving 2-arylated hydronaphthylamines in a highly diastereoselective manner is described. Later, the 2-arylated hydronaphthylamines were converted into highly sensitive 13,14-dehydro benzophenanthridine derivatives by HCl hydrolysis. Further, 13,14-dehydro benzophenanthridines were aromatized into biologically important benzophenanthridine derivatives in the presence of DDQ. A possible reaction mechanism was proposed and supported by deuterium labeling studies and isolation of a rhodacycle intermediate.