Synthetic strategies for the ibophyllidine alkaloids.

Covering: 1975-2020The ibophyllidine alkaloids are unique pyrroloindole alkaloids exhibiting a five-membered D-ring in contrast to the six-membered D-ring of the more common Aspidosperma and Strychnos alkaloids. This structural feature has made them sought-after targets for organic chemists as well as for the elucidation of their biosynthesis. Beginning with the first and eponymous member ibophyllidine, isolation and structure determination is discussed.

Synthesis of Aspidodispermine via Pericyclic Framework Reconstruction.

A divergent approach to the pyrroloquinoline scaffold as present in the class of alkaloids was developed. As a case study, abundant and renewable nicotinic acid was transformed via pericyclic framework reconstruction into aspidodispermine, a unique member of pyrroloquinoline alkaloids. The sequence comprises a [2 + 2]-photocycloaddition, a Ramberg-Bäcklund contraction, and a strain-promoted formal electrocyclic rearrangement of a bicyclo[2.

Taxane Meets Propellane: First Chemical Synthesis of Highly Complex Diterpene Canataxpropellane.

The features of two iconic chemical classes are united in the structure of the highly complex diterpene canataxpropellane and set a daunting challenge that has been met by the Gaich group. Their daring strategy and its benefit to the field of terpene chemistry is presented and discussed in this Highlight.

Rearranged ergostane-type natural products: chemistry, biology, and medicinal aspects.

Classical steroids are long-known privileged leads in drug discovery. Their rearranged counterparts, though, have so far received less attention, although recent isolation and biological testing programmes have revealed a plethora of molecular entities that are both structurally intriguing, as well as biologically relevant. This review will highlight those natural products, and focus on ergostane-derived seco- and abeo-steroids.

Relay Catalysis: Manganese(III) Phosphate Catalyzed Asymmetric Addition of β-Dicarbonyls to ortho-Quinone Methides Generated by Catalytic Aerobic Oxidation.

The combination of an in situ formed MnL complex (HL = Hacac or R(C═O)CHCOR) and a chiral phosphoric acid HX* allows for a fully catalytic, asymmetric synthesis of 4H-chromenes starting from 2-alkyl-substituted phenols. The aerobic oxidation toward a transient ortho-quinone methide was efficiently catalyzed by a manganese(III) species MnL while the ensuing Michael addition of β-dicarbonyl compounds proved to be catalyzed by a chiral manganese phosphate MnLX*.

Identification of Fc Gamma Receptor Glycoforms That Produce Differential Binding Kinetics for Rituximab.

Fc gamma receptors (FcγR) bind the Fc region of antibodies and therefore play a prominent role in antibody-dependent cell-based immune responses such as ADCC, CDC and ADCP. The immune effector cell activity is directly linked to a productive molecular engagement of FcγRs where both the protein and glycan moiety of antibody and receptor can affect the interaction and in the present study we focus on the role of the FcγR glycans in this interaction. We provide a complete description of the glycan composition of Chinese hamster ovary (CHO) expressed human Fcγ receptors RI (CD64), RIIa (CD32a), RIIb (CD32b) and RIIIa (CD16a) and analyze the role of the glycans in the binding mechanism with IgG.