Approaches to the Synthesis of Cytochalasans Part9. A versatile concept leading to all structural types of cytochalasans

Synthesis of cytochalasan analogues with aryl substituents at position 10

Cytochalasans are fungal metabolites that are known to inhibit actin polymerization. Despite their remarkable bioactivity, there are few studies on the structure-activity relationship (SAR) of the cytochalasan scaffold. The full potential of structural modifications remains largely unexplored. The substituent at position 10 of the cytochalasan scaffold is derived from an amino acid incorporated into the cytochalasan core, thus limiting the structural variability at this position in natural products. Additionally, modifications at this position have only been achieved through semisynthetic or mutasynthetic approaches using modified amino acids. This paper introduces a modular approach for late-stage modifications at position 10 of the cytochalasan scaffold. Iron-mediated cross-coupling reactions with corresponding Grignard reagents were used to introduce aryl or benzyl groups in position 10, resulting in the synthesis of six new cytochalasan analogues bearing non-natural aromatic residues. This methodology enables further exploration of modifications at this position and SAR studies among cytochalasan analogues.

Substituted 6-(1-Pyrrolidine)quinolin-2(1H)-ones as Novel Selective Androgen Receptor Modulators

The androgen receptor is a ligand inducible transcription factor that is involved in a broad range of physiological functions. Here we describe the discovery of a new class of orally available selective androgen receptor modulators. The lead compound, 6-[(2R,5R)-2-methyl-5-((R)-2,2,2-trifluoro-1-hydroxyethyl)pyrrolidin-1-yl]-4-trifluoromethylquinolin-2(1H)-one (6a), showed excellent anabolic activity in muscle with reduced effect on the prostate in a rat model of hypogonadism. The compound also improved bone strength in a rat model of post-menopausal osteoporosis.

Synthesis of alpha,beta-unsaturated gamma-lactams via asymmetric iridium-catalysed allylic substitution

Syntheses of alpha,beta-unsaturated gamma-lactams are described that are based on ring-closing metathesis in combination with enantioselective Ir-catalysed allylic amination using N-Boc-N-(but-2-enoyl)-amine as a pronucleophile. As an example application, the synthesis of a Baclofen analogue is presented.

Copper(i) mediated cross-coupling of amino acid derived organozinc reagents with acid chlorides

This paper describes the development of a straightforward experimental protocol for copper-mediated cross-coupling of amino acid derived beta-amido-alkylzinc iodides 1 and 3 with a range of acid chlorides. The present method uses CuCN.2LiCl as the copper source and for organozinc reagent 1 the methodology appears to be limited to reaction with more stable acid chlorides, providing the desired products in moderate yields. When applied to organozinc reagent 3, however, the protocol is more general and provides the products in good yields in all but one of the cases tested.

An efficient synthesis of achiral and chiral 1,2,4-triazolium salts: bench stable precursors for N-heterocyclic carbenes

[reaction: see text] The promising utility of triazolyl N-heterocyclic carbene catalysts in umpolung aldehyde chemistry requires a straightforward reliable synthesis from readily available materials. Herein, we describe the synthesis of a variety of triazolyl N-heterocyclic carbene precursors. The reactions commence from commercially available amino acids and proceed in 44-68% overall yields. The N-heterocyclic salts are air-stable crystalline solids that can be stored with no special precaution and can generate the active catalyst when treated with an appropriate base.

A practical and improved synthesis of (3S,5S)-3-[(tert-butyloxycarbonyl)methyl]- 5-[(methanesulfonyloxy)methyl]-2- pyrrolidinone

A practical and improved synthesis of (3S,5S)-3-[(tert-butyloxycarbonyl)methyl]-5-[(methanesulfonyloxy)methyl]-2-pyrrolidinone (1) is described. The key transformations involve a highly efficient reaction sequence consisting of ethoxycarbonylation, alkylation, hydrolysis, and decarboxylation to produce compound 10. The process described herein is practical, robust, and cost-effective, and it has been successfully implemented in a pilot plant to produce a multikilogram quantity of mesylate 1.

Synthesis of pyrrolidinone PNA: a novel conformationally restricted PNA analogue

To preorganize PNA for duplex formation, a new cyclic pyrrolidinone PNA analogue has been designed. In this analogue the aminoethylglycine backbone and the methylenecarbonyl linker are connected, introducing two chiral centers compared to PNA. The four stereoisomers of the adenine analogue were synthesized, and the hybridization properties of PNA decamers containing one analogue were measured against complementary DNA, RNA, and PNA strands. The (3S,5R) isomer was shown to have the highest affinity toward RNA, and to recognize RNA and PNA better than DNA. The (3S,5R) isomer was used to prepare a fully modified decamer which bound to rU10 with only a small decrease in Tm (delta Tm/mod = 1 degree C) relative to aminoethylglycine PNA.