Synthesis of piperazinones and benzopiperazinones from 1,2-diamines and organoboronic acids

Two decades of recent advances of Passerini reactions: synthetic and potential pharmaceutical applications

This perspective describes the applications of Passerini reactions in the last two decades from 2000 to 2021 in pharmaceutical applications and synthesis of peptides, natural products, macrocycles, dendrimers, and versatile types of heterocycles.

The acid promoted Petasis reaction of organotrifluoroborates with imines and enamines

The acid promoted addition of organotrifluoroborate salts to imine and enamine electrophiles is reported. Use of the pre-activated trifluoroboronate complex bypasses the need for α-hetero substitution on the electrophile component, greatly expanding the scope of the Petasis borono-Mannich reaction. A variety of vinyl, aromatic and heteroaromatic trifluoroborate salts undergo addition with good efficiency under mild reaction conditions. The reaction is amenable for use with a variety of carbamate protected imine and enamine electrophiles, achieving for the first time the effective coupling with aliphatic aldehydes.

Sonochemistry – an innovative opportunity towards a one-pot three-component synthesis of novel pyridylpiperazine derivatives catalysed by meglumine in water

An unprecedented and expeditious synthetic strategy for rapid access to a diversity-oriented library of novel functionalized pyridyl piperazine derivatives is reported.

Component-selective and stereocontrolled one-step three-component reaction among aldehydes, amines, and allenyl boronic acids or allenyl pinacolboronates

A one-step, three-component condensation of allenyl boronic acids or allenyl pinacolboronates with amines and aldehydes affords α-allenyl or α-propargyl α-amino acids and anti-β-amino alcohols. This process gives the allenyl or propargyl product depending on the amine and boron components. Secondary amines generate exclusively α-allenyl α-amino acids, while primary aliphatic amines lead to α-propargyl α-amino acids. Secondary aliphatic amines react with chiral α-hydroxy aldehydes and allenyl boron derivatives to form stereoselectively allenyl anti-β-amino alcohol products.

Lewis acid promoted highly diastereoselective Petasis Borono-Mannich reaction: efficient synthesis of optically active β,γ-unsaturated α-amino acids

An efficient and straightforward method for the preparation of highly enantiomerically enriched β,γ-unsaturated α-amino acid derivatives by a Lewis acid promoted diastereoselective Petasis reaction of vinylboronic acid, N-tert-butanesulfinamide, and glyoxylic acid has been developed. The synthetic utilities of the approach were demonstrated by the rapid and convenient construction of challenging cyclopenta[c]proline derivatives.

A novel route to synthesize libraries of quinoxalines via Petasis methodology in two synthetic operations

This communication reveals an innovative and facile procedure to prepare quinoxalines in two synthetic steps. The microwave assisted Petasis reaction is followed by the acid mediated unmasking of an internal amino nucleophile, cyclodehydration and oxidation to give collections of quinoxalines in good to excellent yields.

Anomalies in the Stereoselectivity of the Petasis Reaction Using Styrenyl Boronic Acids

The Petasis three-component coupling reaction of N-benzylphenylglycinol, glyoxylic acid, and styrenylboronic acids allows for the efficient synthesis of functionalized homoarylalanine derivatives. The reactions were shown to proceed in high yield but low selectivity, regardless of the nature of the substituent on the styrenylboronic acid component. Anomalies in the stereoselectivity of these reactions compared with previously reported results have been traced to the source of the organoboronic acid. Asymmetric dihydroxylation of the unsaturated amino acid derivatives enables a highly efficient route to dihydroxyhomoarylalanine derivatives.

One-pot synthesis of new substituted 1,2,3,4-tetrahydrocarbazoles via Petasis reaction

The one-pot synthesis of a new substituted 1,2,3,4-tetrahydrocarbazoles has been described via Petasis reactions. These tetrahydrocarbazoles exhibits various medicinal importance and might be suitable for elaboration into larger peptides at carboxy termini. The scope and limitations of this method have been examined.

Novel chimeric histone deacetylase inhibitors: a series of lapatinib hybrides as potent inhibitors of epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and histone deacetylase activity

Reversible lysine-specific acetylation has been described as an important posttranslational modification, regulating chromatin structure and transcriptional activity in the case of core histone proteins. Histone deacetylases (HDAC) are considered as a promising target for anticancer drug development, with 2a as pan-HDAC inhibitor approved for cutanous T-cell lymphoma therapy and several other HDAC inhibitors currently in preclinical and clinical development. Protein kinases are a well-established target for cancer therapy with the EGFR/HER2 inhibitor 5 approved for treatment of advanced, HER2 positive breast cancer as a prominent example. In the present report, we present a novel strategy for cancer drug development by combination of EGFR/HER2 kinase and HDAC inhibitory activity in one molecule. By combining the structural features of 5 with an (E)-3-(aryl)-N-hydroxyacrylamide motif known from HDAC inhibitors like 1 or 3, we obtained selective inhibitors for both targets with potent cellular activity (target inhibition and cytotoxicity) of selected compounds 6a and 6c. By combining two distinct pharmacologically properties in one molecule, we postulate a broader activity spectrum and less likelihood of drug resistance in cancer patients.

Influence of an additional amino group on the potency of aminoadamantanes against influenza virus A. II - Synthesis of spiropiperazines and in vitro activity against influenza A H3N2 virus

Spiro[piperidine-2,2'-adamantane] 4 is one of the most potent synthetic anti-influenza A aminoadamantanes or other cage structure amines tested so far. Based on previous results Tataridis et al. (2007) [5h] which demonstrate the boost of in vitro potency by the presence of an additional amino group, we examined whether the incorporation of a second amino group into this heterocycle would increase the anti-influenza A virus activity. The new synthetic molecules 5-7 are capable of forming two hydrogen bonds within the receptor. We identified the diamino derivatives 5 and 6, which are active against influenza A H3N2 virus although less potent than amantadine and its equipotent spiropiperidine 4.

Design of chimeric histone deacetylase- and tyrosine kinase-inhibitors: a series of imatinib hybrides as potent inhibitors of wild-type and mutant BCR-ABL, PDGF-Rbeta, and histone deacetylases

Inhibitors of histone deacetylases are a new class of cancer therapeutics with possibly broad applicability. Combinations of HDAC inhibitors with the kinase inhibitor 1 (Imatinib) in recent studies showed additive and synergistic effects. Here we present a new concept by combining inhibition of protein kinases and HDACs, two independent pharmacological activities, in one synthetic small molecule. In general, the HDAC inhibition profile, the potencies, and the probable binding modes to HDAC1 and HDAC6 were similar as for 6 (SAHA). Inhibition of Abl kinase in biochemical assays was maintained for most compounds, but in general the kinase selectivity profile differed from that of 1 with nearly equipotent inhibition of the wild-type and the Imatinib resistant Abl T(315)I mutant. A potent cellular inhibition of PDGFR and cytotoxicity toward EOL-1 cells, a model for idiopathic hypereosinophilic syndrome (HES), are restored or enhanced for selected analogues (12b, 14b, and 18b). Cytotoxicity was evaluated by using a broad panel of tumor cell lines, with selected analogues displaying mean IC(50) values between 3.6 and 7.1 muM.

Asymmetric petasis reactions catalyzed by chiral biphenols

Chiral biphenols catalyze the enantioselective Petasis reaction of alkenyl boronates, secondary amines, and ethyl glyoxylate. The reaction requires the use of 15 mol % of (S)-VAPOL as the catalyst, alkenyl boronates as nucleophiles, ethyl glyoxylate as the aldehyde component, and 3 A molecular sieves as an additive. The chiral alpha-amino ester products are obtained in good yields (71-92%) and high enantiomeric ratios (89:11-98:2). Mechanistic investigations indicate single ligand exchange of acyclic boronate with VAPOL and tetracoordinate boronate intermediates.

Stereoselectivity of the Petasis reaction with various chiral amines and styrenylboronic acids

Several chiral amines were investigated for the stereoselective preparation of homophenylalanine derivatives using the Petasis reaction. Chiral secondary amines such as N,α-dimethylbenzylamine and N-benzylphenylglycinol gave the best results in terms of both yield and diastereoselectivity. The use of N-benzylphenylglycinol leads directly to 3-alkenyl-4-benzyl-5-phenyloxazin-2-one products. Intriguing variation was observed in the stereoselectivity of reactions employing para-substituted styrenylboronic acid substrates, where presumably only electronic factors are involved.

Phosphinite- and phosphite-based Type I palladacycles as highly active catalysts for addition reactions of arylboronic acids with aldehydes, α,β-unsaturated ketones, α-ketoesters, and aldimines

Phosphinite- and phosphite-based Type I palladacycle-catalyzed additions of arylboronic acids with aldehydes, α,β-unsaturated ketones, α-ketoesters and aldimines are described. Our study showed that readily available phosphinite- and phosphite-based Type I palladacycles could possess higher catalytic activity than phosphine-based palladacycles and were highly active, practical catalysts. Our study may pave the road for development of optically active phosphinite- and phosphite-based palladacycles for asymmetric catalysis.

Organoboron Reagents in the Preparation of Functionalized ?-Amino Acids

Over the past decade, major advances in the preparation and utilization of organoboron reagents have been applied to virtually all areas of organic synthesis. The present review collates recent examples of the use of organoboron reagents in the synthesis of α-amino acids and their derivatives. Aryl- and alkenylboronic acids have been used in the asymmetric synthesis of α-amino acids through conjugate addition to unsaturated amino acids and the Petasis three-component coupling reaction. Additionally, α-amino acid derivatives with organoboron functionality on the side-chain have been prepared and used in metal-catalyzed cross-coupling reactions to prepare cross-linked amino acids and complex cyclic peptide natural products.

Asymmetric multicomponent reactions (AMCRs): the new frontier

Asymmetric multicomponent reactions involve the preparation of chiral compounds by the reaction of three or more reagents added simultaneously. This kind of addition and reaction has some advantages over classic divergent reaction strategies, such as lower costs, time, and energy, as well as environmentally friendlier aspects. All these advantages, together with the high level of stereoselectivity attained in some of these reactions, will force chemists in industry as in academia to adopt this new strategy of synthesis, or at least to consider it as a viable option. The positive aspects as well as the drawbacks of this strategy are discussed in this Review.

Synthesis of bi- and tricyclic arylboronates via Cp*RuCl-catalyzed cycloaddition of α,ω-diynes with ethynylboronate

In the presence of 5-10 mol% Cp*RuCl(cod), 1,6- and 1,7-diynes were allowed to react with an ethynylboronate at ambient temperature to give rise to bi- and tricyclic arylboronates in 64-93% isolated yields.