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Polysubstituted nine-membered-ring lactones are prepared by Ugi reaction of enantiomerically enriched cyclic hemiacetals with a wide range of α-amino acids and isocyanides of aliphatic, peptidic, glycosidic, and lipidic nature.

The copper-catalyzed 1,3-dipolar cycloaddition of alkynyl peptides to azidosteroids allows the synthesis of triazole-linked peptide-steroid conjugates in high yields.

Chiral hydrogen-bond donors have played a crucial role in the progress of asymmetric catalysis as an essential tool in modern organic synthesis. Among these donors, thioureas have been found to be one of the most powerful systems in organocatalytic approaches. Within the last three years, a new generation of bifunctional thiourea catalysts has emerged as an effective way to promote highly demanding chemical transformations, frequently with success rates that are intriguingly higher than with other traditional thioureas. This new class of organocatalysts incorporates a bulky, rigid, and chiral terpene skeleton as one of the thiourea substituents, thus providing an additional and effective rigidifying (entropic) effect on the electrophile activation profile of thioureas. Structural integrations, either with additional Lewis basic nucleophile-activating motifs or with amino groups for enamine catalysis, have enabled their implementation in a wide repertoire of stereocontrolled catalytic processes. This Review charts the development of these new catalysts, as well as their applications in a wide variety of reactions and reaction sequences, with the hope of encouraging further progress in the field of thiourea-catalyst discovery and of bringing attention to the countless possibilities that are opened up by the tremendous success of terpene-derived thiourea catalysts.

Diarylprolinol silyl ethers are used as organocatalysts in asymmetric epoxidation reactions of α,β-unsaturated aldehydes affording optically active epoxides (II) in high yields.

Multicomponent reactions (MCRs) that provide in the final product amides are suitable to produce peptides and peptide-like moieties. The Passerini and Staudinger reactions provide one amide bond, and the Ugi-four-component reaction generates two amides from three or even four (or more) components, respectively. The Ugi-reaction thus is most important to produce peptides and peptoids while the Passerini reaction is useful to generate depsipeptoid moieties. In order to produce cyclic peptides and pseudopeptides, the linear peptidic MCR products have to be cyclized, usually with the help of bifunctional or activatable building blocks. Orthogonal but cyclizable secondary functionalities that need no protection in isonitrile MCRs commonly include alkenes (for ring closing metathesis), azide/alkyne (for Huisgen click reactions) or dienes and enoates (Diels-Alder) etc. If MCR-reactive groups are to be used also for the cyclisation, monoprotected bifunctional building blocks are used and deprotected after the MCR, e.g. for Ugi reactions as Ugi-Deprotection-Cyclisation (UDC). Alternatively one of the former building blocks or functional groups generated by the MCR can be activated. Most commonly these are activated amides (from so-called convertible isonitriles) which can be used e.g. for Ugi-Activation-Cyclisation (UAC) protocols, or most recently for a simultaneous use of both strategies Ugi-Deprotection/Activation-Cyclisation (UDAC). These methods mostly lead to small, medicinally relevant peptide turn mimics. In an opposing strategy, the MCR is rather used as ring-closing reaction, thereby introducing a (di-)peptide moiety. Most recently these processes have been combined to use MCRs for both, linear precursor synthesis and cyclisation. These multiple MCR approaches allow the most efficient and versatile one pot synthesis of macrocyclic pseudopeptides known to date.

Homogeneous non-aqueous permanganate dihydroxylation is used to synthesize spirostanic analogues of brassinosteroids bearing a variety of oxygen functions on ring B.