Diastereodivergent Synthesis of Chiralvic-Disubstituted-Cyclobutane Scaffolds: 1,3-Amino Alcohol and 1,3-Diamine Derivatives - Preliminary Use in Organocatalysis

Expanding the Chemical Space of 1,2-Difunctionalized Cyclobutanes

An efficient approach to the synthesis of previously unavailable or hardly accessible 1,2-difunctionalized cyclobutanes (mostly with NH₂/NHBoc, OH, SH, or SO₂F groups attached to the carbocycle either directly or via a CH₂ unit) relying on the divergent strategy is described. This class of compounds provides sp³-enriched and conformationally restricted building blocks that are of special demand for medicinal chemistry. The target compounds were prepared not only as pure racemic (±)-cis- and (±)-trans-diastereomers but in some cases also as single enantiomers. The developed procedures are readily scaled up and allow obtaining the target compounds on an up to hundred-gram scale. On the basis of the results of 20 X-ray diffraction experiments, structural characterization of the 1,2-difunctionalized cyclobutane core was performed using the extended Cremer-Pople puckering parameters and exit vector (EVP) plots.

(S)-N1,N3-Dibenzyl-1-cyclohexyl-N1,N3-bis((R)-1-phenylethyl)propane-1,3-diamine

(S)-N1,N3-dibenzyl-1-cyclohexyl-N1,N3-bis((R)-1-phenylethyl)propane-1,3-diamine was prepared in good yield by the reduction of the corresponding amide, which was obtained by the addition of a chiral lithium amide to an α,β-unsaturated ester. The target compound was fully characterized by NMR (1H and 13C), high-resolution mass spectrometry and polarimetry.

The Aldol-Tishchenko Reaction of Butanone, Cyclobutanone and a 3-Pentanone Derived Sulfinylimine and DFT Calculations of the Stereo-determining Step

Herein, we present a highly diastereoselective method to furnish acyclic 3-amino-1,5-diol derivatives using a tandem double-aldol-Tishchenko protocol (dr up to >99 : 1) using a butanone derived sulfinylimine. In most cases only 1 diastereomer predominates, from a possible 16. The reaction is also regioselective. In addition, the highly challenging cyclobutanone and 3-pentanone derivatives are also amenable to a double-aldol-Tishchenko reaction, although the dr values are modest. Despite that, clean single diastereomers can be isolated, which should prove very useful in medicinal chemistry and other areas. Detailed DFT calculations support the observed stereoselectivities in all cases, providing a rationale for the excellent dr values in the butanone series and the moderate values for the 3-pentanone class.

New bifunctional 1,3-diamine organocatalysts derived from (+)-camphoric acid for asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroolefins

Novel 1,3-diamine-derived bifunctional thiourea and squaramide organocatalysts were synthesized from (+)-camphoric acid. These catalysts were easily obtained in up to two to five synthetic steps, in a flexible approach that facilitates their structure variation. Their catalytic activity was examined in the asymmetric Michael addition of 1,3-dicarbonyl compounds to several trans-β-nitrostyrenes. Yields up to 98% and enantiomeric excesses up to 74% and high diastereoselectivities when applicable (dr up to 93:7) were obtained in these reactions showing that 1,3-diamine-derived bifunctional thioureas are efficient organocatalysts.

Cyclobutane-Containing Scaffolds as Useful Intermediates in the Stereoselective Synthesis of Suitable Candidates for Biomedical Purposes: Surfactants, Gelators and Metal Cation Ligands

Efficient and versatile synthetic methodologies are reported for the preparation of products that are suitable candidates to be used as surfactants, gelators for hydroxylic solvents or metal cation ligands, with potential use in several fields including biomedical applications. The common structural feature of all the synthesized products is the presence of a cis or trans-1,2- or cis-1,3-difunctionalized cyclobutane ring. In the two first cases, the key intermediates including enantiomerically pure 1,3-diamines and 1,3-amino alcohols have been prepared from β-amino acid derivatives obtained, in turn, from a chiral half-ester. This compound is also precursor of γ-amino esters. Furthermore, two kind of polydentate ligands have also been synthesized from a symmetric 1,5-diamine obtained from norpinic acid, which was easily prepared from commercial verbenone.

Alicyclic β- and γ-Amino Acids: Useful Scaffolds for the Stereocontrolled Access to Amino Acid-Based Carbocyclic Nucleoside Analogs

Stereocontrolled synthesis of some amino acid-based carbocyclic nucleoside analogs containing ring C=C bond has been performed on β- and γ-lactam basis. Key steps were N-arylation of readily available β- or γ-lactam-derived amino ester isomers and amino alcohols with 5-amino-4,6-dichloropyrimidine; ring closure of the formed adduct with HC(OMe)₃ and nucleophilic displacement of chlorine with various N-nucleophiles in the resulting 6-chloropurine moiety.

Selective Synthesis of Fluorine-Containing Cyclic β-Amino Acid Scaffolds

Fluorine-containing organic molecules have generated increasing impact in drug research over the past decade. Their preparation and development of novel synthetic methods towards new types of fluorinated molecules among them of β-amino acid derivatives has received large interest. Our research group have designed various highly selective and stereocontrolled methods for the construction of fluorine-containing cyclic β-amino acid derivatives. The synthetic approaches developed for the synthesis of various pharmacologically interesting cyclic β-amino acid derivatives as monomers with multiple stereogenic centers might be valuable protocols for the access of other classes of organic compounds.

Chemoselective, Substrate-directed Fluorination of Functionalized Cyclopentane β-Amino Acids

This work describes a substrate-directed fluorination of some highly functionalized cyclopentane derivatives. The cyclic products incorporating CH₂ F or CHF₂ moieties in their structure have been synthesized from diexo- or diendo-norbornene β-amino acids following a stereocontrolled strategy. The synthetic study was based on an oxidative transformation of the ring carbon-carbon double bond of the norbornene β-amino acids, followed by transformation of the resulted "all cis" and "trans" diformyl intermediates by fluorination with "chemodifferentiation".

Synthetic methods for 1,3-diamines

In this review, the synthetic methods for the preparation of 1,3-diamines and their applications in synthetic organic chemistry are summarized.

An insight into the synthesis of novel aryl-substituted alicyclic β-amino acid derivatives through substrate-directed palladium-catalysed regio- and stereoselective cross-coupling

Novel aryl-substituted alicyclic β-amino acid derivatives were synthesized through substrate-determined palladium-catalysed cross-coupling of aryl iodides with five- or six-membered cycloalkene β-amino esters.

Simple 1,3-diamines and their application as ligands in ruthenium(ii) catalysts for asymmetric transfer hydrogenation of aryl ketones

A new efficient synthesis of 1,3-diamines was realized and their ruthenium(ii) complexes were studied in ATH in aqueous media.