The first example of ring-closing olefin metathesis of dehydroamino acids: an application to the synthesis of azabicyclo[X.Y.0]alkanes

Cu-mediated enamide formation in the total synthesis of complex peptide natural products

Cu-mediated C(sp(2))-N bond formation has received intense interest recently, and has been applied to the total synthesis of a wide variety of structurally complex natural products. This review covers the synthetic assembly of peptide natural products in which Cu-mediated enamide formation is the key transformation. The total syntheses of cyclopeptide alkaloids, pacidamycin D, and yaku'amide A exemplify the versatility of the Cu-catalyzed cross-coupling reaction in comparison to other synthetic methods.

Desymmetrization of 7-azabicycloalkenes by tandem olefin metathesis for the preparation of natural product scaffolds

Background

Tandem olefin metathesis sequences are known to be versatile for the generation of natural product scaffolds and have also been used for ring opening of strained carbo- and heterocycles. In this paper we demonstrate the potential of these reactions for the desymmetrization of 7-azabicycloalkenes.

Results

We have established efficient protocols for the desymmetrization of different 7-azabicycloalkenes by intra- and intermolecular tandem metathesis sequences with ruthenium based catalysts.

Conclusion

Desymmetrization of 7-azabicycloalkenes by olefin metathesis is an efficient process for the preparation of common natural product scaffolds such as pyrrolidines, indolizidines and isoindoles.

A Versatile Annulation Protocol toward Novel Constrained Phosphinic Peptidomimetics

The development of a novel 3-center 2-component annulation reaction between alpha,omega-carbamoylaldehydes and suitably monoalkylated phosphinic acids is reported. Depending on the starting alpha,omega-carbamoylaldehyde, diverse phosphinic scaffolds varying in the size of their rigidity element, the nature and stereochemistry of substituents, and the participation of heteroatoms in the azacyclic ring system can be obtained in one synthetic step and in high yield. In addition, this methodology allows the synthesis of Fmoc-protected constrained aminophosphinic acids that can be easily converted to suitable pseudodipeptide building blocks compatible with the requirements of peptide synthesis on the solid phase. Finally, the careful choice of both substituents and protecting groups can provide functionally diverse, orthogonally protected constrained scaffolds for extended derivatization of the target phosphinic peptidomimetic structures.

Azabicycloalkenes as Synthetic Intermediates − Synthesis of Azabicyclo[X.3.0]alkane Scaffolds

A general method to synthesize functionalized azabicyclo[X.3.0]alkane scaffolds 5 is reported. Key intermediates are azabicycloalkenes such as 1 and 2, which are acylated with unsaturated carboxylic acids and subsequently submitted to tandem olefin metathesis. The resulting bicyclic heterocycles are versatile intermediates for different dipeptide mimetics and can be used as intermediates for natural products with indolizidine scaffolds or analogues thereof. [reaction: see text].