The rhodium-catalyzed asymmetric N-selective and regioselective coupling of triazole derivatives with internal alkynes and terminal allenes gives access to secondary and tertiary allylic triazoles in very good enantioselectivities. For this process, three new members of the JosPOphos ligand family have been prepared and employed in catalysis. The optimized reaction conditions enable the coupling of triazoles with internal alkynes as well as with allenes, displaying a high tolerance for functional groups. A gram scale reaction provided N-allyltriazole, which was subjected to various transformations highlighting synthetic utility.

Concise syntheses of the Hancock alkaloids (−)-angustureine and (−)-cuspareine are presented, applying and refining a recently developed rhodium-catalyzed hydroamination for the stereoselective construction of the chiral secondary amine. Furthermore, the syntheses include an allene synthesis via boron–magnesium exchange as well as the construction of the tetrahydroquinoline motive via a hydroboration/Suzuki–Miyaura coupling sequence.

A rhodium-catalyzed regio- and enantioselective cyclization of tethered allenylbenzenes is reported.

A short and efficient total synthesis of the C -symmetric (-)-cylindrocyclophane F is presented, using a cross olefin metathesis dimerization strategy for construction of the [7,7]-paracyclophane macrocycle. The synthesis of the dimerization building block includes a Pd-catalyzed sp -sp Negishi cross coupling of a sterically hindered Zn-reagent with an aromatic triflate, an enantiospecific Zn-catalyzed sp -sp cross coupling of an α-hydroxy ester triflate with a Grignard reagent and the application of an enantioselective Rh-catalyzed C-allylation of an electron rich arene.

Natural products of polyketide origin, in particular small-sized lactones often possess a very broad range of impressive biological activities. An efficient way to demonstrate the concise access to six-membered lactones was emphasized as part of a stereodivergent and protecting-group-free synthesis of all three representatives of the helicascolide family. This strategy features an atom-economical and highly diastereoselective rhodium-catalyzed "head-to-tail" lactonization by an intramolecular addition of ω-allenyl-substituted carboxylic acids to terminal allenes, including the selective construction of a new stereocenter in the newly formed core structures. The excellent selectivities with which the helicascolide precursors were obtained are remarkable, thus resulting in an expeditious and highly efficient natural product synthesis.

Scheme 1. Industrial process for the synthesis of (R)-(À )-Sitagliptin (1) developed by DSM and Codexis.

The rhodium-catalyzed asymmetric intramolecular hydroamination of sulfonyl amides with terminal allenes is reported. It provides selective access to 5-and 6-membered Nheterocycles,s caffolds found in al arge range of different bioactive compounds.M oreover,g ram scale reactions,a sw ell as the application of suitable product transformations to natural products and key intermediates thereof are demonstrated.

Cylindrocyclophanes are a class of naturally occurring 22-membered macrocycles with a unique architecture and interesting physical, chemical, and biological properties. This comprehensive account summarizes progress in various synthetic approaches to these compounds during the last twenty years, thereby emphasizing the key steps for establishing the [7,7]-paracyclophane scaffold, as well as alternative approaches to the construction of its stereocenters. Many of these syntheses highlight the power of transition-metal catalysis for natural-product synthesis. Furthermore, the unraveling of the biosynthesis to these natural products in Cylindrospermum licheniforme is discussed.1 Introduction2 Biosynthesis3 Smith’s Synthesis of (–)-Cylindrocyclophanes A and F4 Hoye’s Synthesis of (–)-Cylindrocyclophane A5 Iwabuchi’s Syntheses of (–)-Cylindrocyclophane A and (+)-Cylindrocyclophane A6 Nicolaou’s Synthesis of (–)-Cylindrocyclophanes A and F7 Breit’s Synthesis of (–)-Cylindrocyclophane F8 Conclusion