A concise enantioselective synthesis of l-(−)-733,061 and (2S,3S)-methyl 3-aminopiperidine-2-carboxylate using catalytic enantioselective aza-Henry reaction as key step

Bis-zirconocenes Generated from Weinreb 2-Allylaminoacetamides as Key Intermediates for a Diastereoselective Approach to 2- and 6-Substituted-3-Aminopiperidines

The synthesis of 2- and 6-substituted-3-aminopiperidines from Weinreb amides containing an allylamino fragment is reported. Involving the simultaneous hydrozirconation of the C═C and the C═O bonds, the cyclization was promoted by the BF3-mediated generation of an iminium. Proven to be highly diastereoselective, the sequence can be applied to diversely substituted unsaturated Weinreb amides and valorized through the preparation of bicyclic heterocycles.

Catalytic asymmetric synthesis of 1,2-diamines

The asymmetric catalytic synthesis of 1,2-diamines has received considerable interest, especially in the last ten years, due to their presence in biologically active compounds and their applications for the development of synthetic building blocks, chiral ligands and organocatalysts. Synthetic strategies based on C-N bond-forming reactions involve mainly (a) ring opening of aziridines and azabenzonorbornadienes, (b) hydroamination of allylic amines, (c) hydroamination of enamines and (d) diamination of olefins. In the case of C-C bond-forming reactions are included (a) the aza-Mannich reaction of imino esters, imino nitriles, azlactones, isocyano acetates, and isothiocyanates with imines, (b) the aza-Henry reaction of nitroalkanes with imines, (c) imine-imine coupling reactions, and (d) reductive coupling of enamines with imines, and (e) [3+2] cycloaddition with imines. C-H bond forming reactions include hydrogenation of CN bonds and C-H amination reactions. Other catalytic methods include desymmetrization reactions of meso-diamines.

The Stereoselective Nitro-Mannich Reaction in the Synthesis of Active Pharmaceutical Ingredients and Other Biologically Active Compounds

The nitro-Mannich (aza-Henry) reaction, in which a nitroalkane and an imine react to form a β-nitroamine, is a versatile tool for target-oriented synthesis. Although the first stereoselective reaction was developed only 20 years ago, and enantioselective and diastereoselective versions for the synthesis of non-racemic compounds soon after, there are nowadays a variety of reliable methods which can be used for the synthesis of APIs and other biologically active substances. Hence many anticancer drugs, antivirals, antimicrobials, enzyme inhibitors and many more substances, containing C-N bonds, have been synthesized using this reaction. Several transition metal complexes and organocatalysts were shown to be compatible with the presence of a wide range of functional groups in these molecules, and very high levels of asymmetric induction have been achieved in some cases. The reaction has also been applied in cascade processes. The structural diversity of the products, ranging from simple heterocycles or azabicycles to complex alkaloids, iminosugars, amino acids or diamino acids and phosphonates, shows the versatility of the nitro-Mannich reaction and its potential for future developments.

Recent synthetic applications of α-amido sulfones as precursors of N-acylimino derivatives

α-Amido sulfones can be directly used as N-acylimine or N-acyliminium ion precursors in several synthetic processes aimed at the preparation of nitrogen containing compounds. This review collects the most relevant and practical utilizations of α-amido sulfones appeared in the literature after 2005.

One-pot multicomponent nitro-Mannich reaction using a heterogeneous catalyst under solvent-free conditions

An environmentally-friendly, one-pot multicomponent reaction of various aldehydes, amines and nitroalkanes for the synthesis of β-nitroamines is here described. Amberlyst A-21 supported CuI was found to be a highly efficient novel heterogeneous catalyst for the three-component nitro-Mannich reaction between aldehydes, amines and nitroalkanes. The developed protocol is performed in a solvent-free medium to produce a variety of β-nitroamines in good to excellent yields within short reaction times. The catalyst can be easily prepared and recovered. It has been tested up to eight times with only a minor activity loss.

Stereodivergent synthesis of 5-aminopipecolic acids and application in the preparation of a cyclic RGD peptidomimetic as a nanomolar αVβ3 integrin ligand

A stereodivergent preparation of trans and cis-5-aminopipecolic acids (5-APAs) was developed to obtain constrained amino acids useful for peptidomimetics.

Stereoselective synthesis of 1,2-diamine containing indolines by a conjugate addition nitro-Mannich reaction

A conjugate addition nitro-Mannich reaction followed by nitro reduction and intramolecular N-arylation gives diastereomerically pure substituted 1,2-diamine containing indolines. Placing the N-arylation cyclisation handle on the imine precursor derived from an ortho-bromine substituted aromatic aldehyde gave the corresponding β-nitroamines in 55-72% yields as single diastereoisomers. Nitro reduction was effected with modified quantities of Zn/HCl and a subsequent Pd(0) catalysed Buchwald Hartwig cyclisation gave indoline products in 40-70% yields as single diastereoisomers.

A concise diastereoselective approach to enantioenriched substituted piperidines and their in vitro cytotoxicity evaluation

A library of diversely stereo-oriented, highly substituted 2,6-cis piperidine derivatives were synthesized, and evaluated for their anticancer activity in cancer cells that included A549 (lung cancer, CCL-185), MCF7 (breast cancer (HTB-22), DU145 (prostate cancer (HTB-81), and HeLa (cervical cancer, CCL-2). One stereo-variant emerged as a promising candidate for further design based structure-activity studies.

Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step

Piperazirum, isolated from Arum palaestinum Boiss, was originally assigned as r-3,c-5-diisobutyl-c-6-isopropylpiperazin-2-one. The reported structure was synthesised diastereoselectively using a key nitro-Mannich reaction to set up the C5/C6 relative stereochemistry. The structure was unambiguously assigned by single crystal X-ray diffraction but the spectroscopic data did not match those reported for the natural product. The structure of the natural product must therefore be revised.

H12461. Fluorine as a Regiocontrol Element in the Ring Openings of Bicyclic Aziridiniums

The origin of the variation in the regioselectivity of the nucleophilic ring-opening of a series of bicyclic aziridinium ions derived from N-alkylprolinols was investigated by quantum chemical computations (M06-2X/6-31+G(d,p)-SMD). These aziridiniums differ only in the degree and the stereochemistry of fluoro substitution at C(4). With the azide ion as nucleophile, the ratio of the piperidine to the pyrrolidine product was computed. An electrostatic gauche effect influences the conformation of the adjoining five-membered ring in the fluorinated bicyclic aziridinium. This controls the regioselectivity of the aziridinium ring-opening.

A new family of cinchona-derived bifunctional asymmetric phase-transfer catalysts: application to the enantio- and diastereoselective nitro-Mannich reaction of amidosulfones

A new family of bifunctional H-bond donor phase-transfer catalysts derived from cinchona alkaloids has been developed and evaluated in the enantio- and diastereoselective nitro-Mannich reaction of in situ generated N-Boc-protected imines of aliphatic, aromatic, and heteroaromatic aldehydes. Under optimal conditions, good reactivity and high diastereoselectivities (up to 24:1 dr) and enantioselectivities (up to 95% ee) were obtained using a 9-amino-9-deoxyepiquinidine-derived phase-transfer catalyst possessing a 3,5-bis(trifluoromethyl)phenylurea H-bond donor group at the 9-position.