98061-21-3

A new series of octahedral rhodium(III) complexes 1–8 of the type [(Ln)2Rh(dppz)]Cl (n = 1–6) and [(Ln)2Rh(dppz)](PF6) {n = 1, 7, 8; L = 2-phenylpyridine, with different modifications, as the C,N-chelating ligand; and dppz = dipyrido[3,2-a:2′,3′-c]phenazine} have been synthesized and fully characterized. The photophysical properties of the complexes have been investigated. The single-crystal X-ray diffraction structures of five complexes – [(L1)2Rh(dppz)](PF6), [(L2)2Rh(dppz)]Cl, [(L3)2Rh(dppz)](PF6), [(L4)2Rh(dppz)](PF6), and [(L8)2Rh(dppz)](PF6) – have confirmed the anticipated structure and have revealed the effect of substitution on the structure of the complex, which has been reasonably explained through experimental electrochemical characterization. The interaction of complexes 1–8 with calf thymus DNA (CT DNA) has been verified by the fluorescent detection of ethidium bromide (EB) displacement studies. The result clearly suggests that the DNA-binding abilities of these Rh complexes are not only influenced by the DNA-intercalator dppz, but are also highly influenced by the electronic and steric properties of the C,N-chelating ligands.

We previously reported the design and synthesis of amphiphilic Ir complex–cationic peptide hybrids (2a–2f), which contain basic peptide sequences such as KKGG (K = lysine, G = glycine) at the 5′-positions (para position with respect to the C–Ir bond) of three 2-(4′-tolyl)pyridine (tpy) ligands. Among them, 2c–2e induced the necrosis-like cell death of Jurkat cells through a calcium-dependent pathway, possibly involving a Ca2+–calmodulin (CaM) complex. Herein, we report the synthesis of amphiphilic Ir(ppy)3 complexes (ppy = 2-phenylpyridine) containing the KKGG sequence at the 4′-position of the ppy moiety (4a??4d) to examine the effect of the position of the cationic peptide sequence on the cytotoxicities of the complexes against Jurkat cells. The results of 3-(4,5-dimethly-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays and a mechanistic study indicate that 4b and 4c, which contain C6 and C8 linkers, induce cell death through a calcium-dependent pathway accompanied by membrane disruption in a manner similar to that of 2c–2e but with smaller half-maximal effective concentration (EC50) values than those of 2c–2e. The results of the photoaffinity labeling of Jurkat cells with 5b containing a photoreactive 3-trifluoromethyl-3-phenyldiazirine (TFPD) unit and co-staining experiments with specific probes for intracellular organelles suggest that 4b and 4c bind to Ca2+–CaM and are localized in the mitochondria during cell death.

The C-H bond addition reaction of 2-phenylpyridine derivatives with α,β-unsaturated carboxylic acids catalyzed by Cp*Rh(iii)/BH3·SMe2is reported. Activation of C-H bonds with the rhodium catalyst and activation of α,β-unsaturated carboxylic acids with the boron catalyst cooperatively work, and a BINOL-urea hybrid ligand significantly improved the reactivity. With the optimized hybrid catalytic system, various β-disubstituted carboxylic acids were obtained under mild reaction conditions.

A novel nickel-catalyzed reductive cross-coupling between aryl iodides and difluoromethyl 2-pyridyl sulfone (2-PySO2CF2H) enables C(sp2)-C(sp2) bond formation through selective C(sp2)-S bond cleavage, which demonstrates the new reactivity of 2-PySO2CF2H reagent. This method employs readily available nickel catalyst and sulfones as cross-electrophile coupling partners, providing facile access to biaryls under mild reaction conditions without pregeneration of arylmetal reagents.

We report a rhodium-catalyzed ortho C(sp2)-H borylation of 2-phenylpyridines using commercially available N-heterocyclic carbenes (NHCs) as ligand and pinacolatodiboron (B2pin2) as borylating reagent. The reaction could take place at room temperature, tolerating a wide range of functionalities and affording ortho borylated products in moderate to excellent yields. The current method is also applicable to gram-scale reaction with reduced catalyst loading.

Addition of catalytic arene C-H to formaldimines has been enabled by Ru(II)-catalyzed amidomethylation with bis(tosylamido)methane as a catalytic formaldimine releaser. The new process provides an atom-efficient and sustainable solution to address the challenges of formaldimines in this type of transformation. Furthermore, new synthetic routes based on this catalytic system have been developed for step-efficient access to N-heterotricyclic core structures that are pharmaceutically relevant.

Multicomponent Mannich reactions through C?H bond activation are described. These transformations allowed for the straightforward generation of densely substituted benzylic and homo-benzylic amines in good yields. The reaction involves a reaction between two transient species: an organometallic species, generated by transition-metal-catalyzed sp2 or sp3 C?H bond activation and an in situ generated imine. The use of an acetal as an aldehyde surrogate was found essential for the reaction to proceed. The process could be successfully applied to RhIII-catalyzed sp2 C?H bond functionalization and extended to CuII-catalyzed sp3 C?H bond functionalization.

Cleavage of carbon-carbon bonds has been found in some important industrial processes, for example, petroleum cracking, and has inspired development of numerous synthetic methods. However, nonpolar unstrained C(aryl)-C(aryl) bonds remain one of the toughest bonds to be activated. As a detailed study of a fundamental reaction mode, here a full story is described about our development of a Ru-catalyzed reductive cleavage of unstrained C(aryl)-C(aryl) bonds. A wide range of biaryl compounds that contain directing groups (DGs) at 2,2′ positions can serve as effective substrates. Various heterocycles, such as pyridine, quinoline, pyrimidine, and pyrazole, can be employed as DGs. Besides hydrogen gas, other reagents, such as Hantzsch ester, silanes, and alcohols, can be employed as terminal reductants. The reaction is pH neutral and free of oxidants; thus a number of functional groups are tolerated. Notably, a one-pot C-C activation/C-C coupling has been realized. Computational and experimental mechanistic studies indicate that the reaction involves a ruthenium(II) monohydride-mediated C(aryl)-C(aryl) activation and the resting state of the catalyst is a η4-coordinated ruthenium(II) dichloride complex, which could inspire development of other transformations based on this reaction mode.

Because of the increase in the number of immunocompromised patients, the incidence of invasive fungal infections is growing, but the treatment efficiency remains unacceptably low. The most potent clinical systemic antifungals (azoles) are the derivatives of two scaffolds: ketoconazole and fluconazole. Being the safest antifungal drugs, they still have shortcomings, mainly because of pharmacokinetics and resistance. Here, we report the successful use of the target fungal enzyme, sterol 14α-demethylase (CYP51), for structure-based design of novel antifungal drug candidates by minor modifications of VNI [(R)-N-(1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethyl)-4-(5-phenyl-1,3,4-oxadiazol-2-yl)benzamide)], an inhibitor of protozoan CYP51 that cures Chagas disease. The synthesis of fungi-oriented VNI derivatives, analysis of their potencies to inhibit CYP51s from two major fungal pathogens (Aspergillus fumigatus and Candida albicans), microsomal stability, effects in fungal cells, and structural characterization of A. fumigatus CYP51 in complexes with the most potent compound are described, offering a new antifungal drug scaffold and outlining directions for its further optimization.

Cp?Rh(NHC) complexes with bulky chiral bidentate NHC-carboxylate ligands were efficiently synthesized and fully characterized including solid-state structures. These unprecedented rhodium(iii) complexes demonstrated high selectivity in pyridine-directed ortho-C-H borylation of arenes under mild conditions.

A facile, transition-metal-free, and direct decarboxylative arylation of 2-picolinic acids with simple arenes is described. The oxidative decarboxylative arylation of 2-picolinic acids with arenes proceeds readily via N-chloro carbene intermediates to afford 2-arylpyridines in satisfactory to good yields under transition-metal-free conditions. This new type of decarboxylative arylation is operationally simple and scalable and exhibits high functional-group tolerance. Various synthetically useful functional groups, such as halogen atoms, methoxycarbonyl, and nitro, remain intact during the decarboxylative arylation of 2-picolinic acids.

The one-step synthesis of the bench-stable hypervalent iodine reagents IndoleBX and PyrroleBX using mild Lewis acid catalyzed conditions is reported. The new reagents are stable up to 150 °C and were applied in the C?H arylation of unactivated arenes using either rhodium or ruthenium catalysts. A broad range of heterocyclic systems of high interest for synthetic and medicinal chemistry was accessed in high yields. The developed C?H functionalization could not be achieved using reported reagents or methods, highlighting the unique reactivity of Indole- and Pyrrole-BX.

The first palladium-catalyzed decarbonylative coupling of phenyl 2-azinecarboxylates and arylboronic acids is presented. The key for the development of this decarbonylative coupling is the use of Pd/dcype as a catalyst. A wide range of 2-azinecarboxylates can undergo the present coupling reaction to afford 2-arylazines. By combination with previously reported nickel-catalyzed decarbonylative coupling, we achieved a chemoselective sequential decarbonylative coupling of pyridine dicarboxylate to synthesize 2,4-diarylpyridine.

Disclosed herein are new compounds and compositions and their application as pharmaceuticals for the treatment of diseases. Methods of inhibition of KDM1A, methods of increasing gamma globin gene expression, and methods to induce differentiation of cancer cells in a human or animal subject are also provided for the treatment of diseases such as acute myelogenous leukemia.

A cobalt-catalyzed C-H cyanation reaction of arenes has been developed using N-cyanosuccinimide as a new electrophilic cyanating agent. The reaction proceeds with high selectivity to afford monocyanated products with excellent functional group tolerance. Substrate scope was found to be broad enough to include a wide range of heterocycles including 6-arylpurines.

We report the synthesis, characterisation and photophysical properties of new phosphorescent biscyclometallated iridium(iii) ethylenediamine (en) complexes functionalised with polar ester or carboxylate groups [Ir(N^C)2(en)]n(X) (n = +1, X = Cl-, HN^C = methyl 4-(2-pyridyl)benzoate Hppy-COOMe (1a), methyl 2-phenyl-4-quinolinecarboxylate Hpq-COOMe (2a); n = -1, X = Li+, HN^C = 4-(2-pyridyl)benzoate Hppy-COO- (1b), 2-phenyl-4-quinolinecarboxylate Hpq-COO- (2b)). In aqueous solutions, the carboxylate complexes 1b and 2b displayed emission quenching (ca. 7 and 74 fold, respectively) and lifetime shortening upon protonation, and their pKa values were determined to be 5.13 and 3.46, respectively. The pq complexes 2a and 2b exhibited hypsochromic shifts in their emission maxima and a significant increase in emission intensity (ca. 84 and 15 fold, respectively) upon nonspecific binding to the protein bovine serum albumin (BSA). Inductively coupled plasma-mass spectroscopy (ICP-MS) and laser-scanning confocal microscopy (LSCM) results revealed that the ester complexes 1a and 2a were efficiently internalised by the human cervix epithelioid carcinoma (HeLa) cells through energy-requiring pathways and subsequently localised in endosomes and mitochondria, respectively. They showed good biocompatibility in the dark, but became significantly cytotoxic upon photoirradiation due to the generation of singlet oxygen. In contrast, in aqueous solutions of physiological pH, the carboxylate complexes 1b and 2b existed as the anionic form and hardly entered cells due to limited membrane permeability, as evidenced by the intense emission surrounding the plasma membrane of the cells. They showed negligible cytotoxicity and the cell viability remained over 95% for an incubation period of 24 hours. In view of the low cytotoxicity and strongly emissive nature of the hydrophilic ppy-COO- complex 1b in an aqueous medium, the potential application of the complex as a visualisation reagent has been demonstrated using zebrafish (Danio rerio) as an animal model. This journal is

A general procedure for the fast Suzuki coupling of major families of heteroaryl bromides was realized by using Pd(OAc)2/PtBu3 as the catalyst. Many couplings were finished within minutes at room temperature in n-butanol. Different from previous studies, three typical heteroaryl bromides were systematically examined in couplings of various heteroaryl and aryl boronic acids. A fast, general coupling of heteroaryl bromides is realized by using a single palladium catalyst supported by tri-tert-butylphosphine.

A Cu-catalyzed aromatic C-H amidation with phthalimide under oxygen as a terminal oxidant without using additional additives has been achieved. This reaction has the broad substrate scope and shows moderate to good yields in most cases. This method is complementary to the previously reported metal-catalyzed C-H amination systems.

Palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of tetrabutylammonium 2-pyridyltriolborate salts with various aryl (heteroaryl) chlorides can produce the corresponding desired coupling products with good to excellent yields. These tetrabutylammonium salts are more reactive than the corresponding lithium salts. The coupling reactions with aryl chlorides progressed in the presence of PdCl2dcpp (3 mol %) and CuI/MeNHCH 2CH2OH (20 mol %) in anhydrous DMF without bases.

The novel palladium-catalyzed decarboxylative cross-coupling reactions of 2-picolinic acid with aryl and heteroaryl bromides including benzenes, naphthalenes, pyridines and quinolines for C-C bond formation have been successfully achieved. This journal is

A Pd(II)-catalyzed C-H phosphorylation reaction has been developed using heterocycle-directed ortho-palladation. Both H-phosphonates and diaryl phosphine oxides are suitable coupling partners for this reaction.

In search of alternatives to unstable or unreliable 2-pyridylboron reagents, we have explored two new varieties of solid, moderately air-stable 2-pyridylzinc reagents. Both reagents can be manipulated in air and are competent nucleophiles in Negishi cross-coupling reactions.

This work highlights unsymmetrical biaryl compounds via direct nickel-catalyzed reductive coupling of two aryl halides. By tuning the ligand structures, the reaction of two electron-enriched aryl halides also provided the coupling product in good yields, with an excess of 1.4 equivalents of one of the halides. The mild reaction conditions display excellent functional-group tolerance and generally gave the coupling products in moderate to good yields. In addition to aryl bromides, activated aryl chlorides are effective.

SIRT1 is an NAD+-dependent deacetylase, whose activators have potential therapeutic applications in age-related diseases. Here we report a new class of SIRT1 activators. The activation is dependent on the fluorophore labeled to the substrate. To elucidate the activation mechanism, we solved the crystal structure of SIRT3/ac-RHKKac-AMC complex. The structure revealed that the fluorophore blocked the H-bond formation and created a cavity between the substrate and the Rossmann fold. We built the SIRT1/ac-RHKK ac-AMC complex model based on the crystal structure. Km and Kd determinations demonstrated that the fluorophore decreased the peptide binding affinity. The binding modes of SIRT1 activators indicated that a portion of the activators interacts with the fluorophore through π-stacking, while the other portion inserts into the cavity or interacts with the Rossmann fold, thus increasing the substrate affinity. Our study provides new insights into the mechanism of SIRT1 activation and may aid the design of novel SIRT1 activators.

We report the direct amidation of arene C-H bonds using sulfonyl azides as the amino source to release N2 as the single byproduct. The reaction is catalyzed by a cationic rhodium complex under external oxidant-free conditions in the atmospheric environment. A broad range of chelate group-containing arenes are selectively amidated with excellent functional group tolerance, thus opening a new avenue to practical intermolecular C-N bond formation.

Rh-catalyzed direct carboxylation of unactivated aryl C-H bond under atmospheric pressure of carbon dioxide was realized via chelation-assisted C-H activation for the first time. Variously substituted and functionalized 2-arylpyridines and 1-arylpyrazoles underwent the carboxylation in the presence of the rhodium catalyst and a stoichiometric methylating reagent, AlMe 2(OMe), to give carboxylated products in good yields. The catalysis is proposed to consist of methylrhodium(I) species as the key intermediate, which undergoes C-H activation to afford rhodium(III), followed by reductive elimination of methane to give nucleophilic arylrhodium(I). This approach demonstrates promising application of C-H bond activation strategy in the field of carbon dioxide fixation.

Copper-mediated intermolecular direct biaryl coupling of arylazines and azoles via dual C-H bond cleavage proceeds even without palladium catalysts. The reaction system shows the high potential of copper salts in direct C-H arylation chemistry and provides a new approach to biaryl motifs, which are ubiquitous in pharmaceuticals and functional materials.

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We present a PdCl2(dppf)-catalyzed synthesis of 2-arylated pyridine derivatives via the in situ coupling of 2-OH pyridines and boronic acids mediated by PyBroP. In addition, the highly chemo- and regioselective construction of two different aryl-aryl bonds via a one-pot operation has also been demonstrated by the orthogonal use of this method with the Ni-catalyzed Suzuki-Miyaura coupling of phenols.

(Graph Presented) Phosphorescent cyclometalated iridium tris(2-phenylpyridine) derivatives were designed and incorporated into coordination polymers as tricarboxylate bridging ligands. Three different crystalline coordination polymers were synthesized using a solvothermal technique and were characterized using a variety of methods, including single-crystal X-ray diffraction, PXRD, TGA, IR spectroscopy, gas adsorption measurements, and luminescence measurements. The coordination polymer built from Ir[3-(2-pyridyl)benzoate]3, 1, was found to be highly porous with a nitrogen BET surface area of 764 m2/g, whereas the coordination polymers built from Ir[4-(2-pyridyl)benzoate]3, 2 and 3, were nonporous. The 3MLCT phosphorescence of each of the three coordination polymers was quenched in the presence of O2. However, only 1 showed quick and reversible luminescence quenching by oxygen, whereas 2 and 3 exhibited gradual and irreversible luminescence quenching by oxygen. The high permanent porosity of 1 allows for rapid diffusion of oxygen through the open channels, leading to efficient and reversible quenching of the 3MLCT phosphorescence. This work highlights the opportunity of designing highly porous and luminescent coordination polymers for sensing other important analytes. Copyright

(Figure Presented) A chelation-assisted copper(II)-catalyzed ortho-acyloxylation of the 2-arylpyridine sp2 C-H bond with anhydride is described. The procedure tolerates various functional groups, such as carbomethoxyl, methoxyl, fluoro, bromo, chloro, and cyano groups, affording the mono- or diacyloxylated products in moderate to good yields. Importantly, this procedure uses O2 as a clean terminal oxidant.

An unprecedented protocol for cyanation at arene C-H bonds has been developed by employing N,N-dimethylformamide and ammonia as a combined source for the cyano "CN" unit. Isotopic incorporation experiments revealed that the carbon and nitrogen of the "CN" originate from the N,N-dimethyl moiety of DMF and ammonia, respectively. The present cyanation reaction shows an excellent degree of regioselectivity, producing only monosubstituted nitriles at the less hindered C-H position, and it allows for the preparation of doubly labeled nitrile compounds for the first time.

A mild Negishi cross-coupling of 2-heterocyclic organozinc reagents and aryl chlorides is described. The use of Pd2(dba)3 and X-Phos as a ligand provides high yields for many examples. An efficient method to generate the organozinc reagents at room temperature is also demonstrated.

(Figure presented) The first example of an iron-mediated direct Suzuki-Miyaura reaction between N-heterocyclic compounds and arylboronic acids is described, and both electron-rich and electron-deficient heteroarenes can be successfully used for the coupling reaction.

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A novel palladium catalyzed direct ortho-arylation of N-phenacylpyridinium bromide was developed. The amazing N-phenacyl group regioselectively activates the C-H bond of pyridine and automatically departs from the arylated products. A kinetic isotope effe

Figure Presented A rhodium-catalyzed ortho-benzoxylation of the sp 2 C-H bond by carboxylic acids is described. The procedure tolerates carbomethoxy, formyl, bromo, chloro, and nitro groups, providing the benzoxylated products in moderate to good yields. Importantly, no external oxidant was required for the transformation.

An efficient nickel-catalyzed method devoted to the direct formation of functionalized 2-arylpyridines is described avoiding the prior preparation of organometallic species. Various functionalized 2-arylpyridines are obtained in moderate to excellent yields by a one-step chemical procedure from corresponding halides. The NiBr2(2,2′-bipyridine) complex appears to be an extremely suitable catalyst for the activation in the presence of manganese dust of aromatic halides and pyridyl halides functionalized by reactive groups. The versatility of this original process represents a simple alternative to most known methods using organometallic reagents.

Palladium-catalysed cross-coupling of 2-trimethylsilylpyridine with aryl halides in the presence of stoichiometric silver(I) oxide, and catalytic TBAF allows the rapid preparation of the corresponding pyridin-2-ylaryl compounds in moderate to good yields

The synthesis of functionalized arylzinc reagents from aromatic chlorides, triflates, or mesylates, via cobalt catalysis, is reported using 2,2′-bipyridine as a ligand in a mixture of acetonitrile and pyridine. This procedure allows the synthesis of a variety of functionalized arylzinc species in good to excellent yields. Some of these arylzinc compounds have been coupled with aromatic bromides under palladium catalysis. Georg Thieme Verlag Stuttgart.

Direct arylation reactions of pyridine N-oxides occur in excellent yield with complete selectivity for the 2-position with a wide range of aryl bromides. This reactivity permits the use of inexpensive, commercially available, and bench-stable pyridine N-oxides as replacements for problematic 2-metallapyridines in palladium-catalyzed cross-coupling reactions. Copyright

Tris(trimethylsilyl)silane (TTMSS) and azabisisobutyronitrile (AIBN) promoted the intermolecular arylation of aryl and heteroaryl bromides onto aromatic solvents under thermal conditions via a radical pathway.

A benzoheterocyclic derivative of the following formula [1]: and pharmaceutically acceptable salts thereof, which show excellent anti-vasopressin activity, vasopressin agonistic activity and oxytocin antagonistic activity, and are useful as a vasopressin antagonist, vasopressin agonist or oxytocin antagonist.

The palladium-catalyzed cross-coupling reactions between arylmagnesium halides (phenylmagnesium chloride, mesitylmagnesium bromide, 4-(methoxycarbonyl)phenylmagnesium chloride and 4-cyanophenylmagnesium chloride) and halopyridines allowed the synthesis of substituted pyridines. Owing to the remarkably mild conditions used (often below 0°C), the reaction could be extended to the use of functionalized halopyridines, haloquinolines and halodiazines.

Soluble polymer-supported chemistry is a technology that allows the blending of the benefits of polymer-supported synthesis and solution-phase chemistry. Herein, we describe our recent efforts in this area targeted at exploring the scope of poly(ethylene glycol) (PEG) as the matrix. Specifically we describe the use of PEG as a support for triphenyl phosphine and for the Stille reaction.

2-Arylpyridines substituted on aryl and/or on pyridine nuclei can be obtained in good to high yields in one step by electroreduction of mixtures of the corresponding aryl and pyridyl halides using the sacrificial iron anode process and a nickel 2,2'-bipyr

The invention relates to a novel process for the preparation of compounds of formula I STR1 wherein R1 is hydrogen or a suitable amino-protecting group, R2 is unsubstituted or substituted alkyl, R3 is hydrogen, aryl, heterocyclyl, unsubstituted or substituted alkyl or unsubstituted or substituted cycloalkyl, R4, independently of R1, is hydrogen or a suitable amino-protecting group and m is a number from 1 to 7; and wherein further suitable protecting groups for functional groups may be present; which compounds are antivirally active or can be used as starting materials for pharmaceutically active, especially antiviral compounds. The precursor is an oxo compound, which is in turn prepared by hydrogenation with a suitable complex hydride or with hydrogen in the presence of a suitable catalyst and acyl migration starting from a hydrazone, which is in turn preferably prepared from a nitrile via an imino compound by means of hydrogenation and reaction with a hydrazine derivative, which is prepared from an aldehyde by reaction with a reactive derivative of a carboxylic acid in the presence of a cyanide salt; and the novel intermediates required therefor.

2-Arylpyridines can be obtained in good to high yields by electrochemical reductin using the sacrificial anode process and catalysis by nickel-2,2'-bipyridine (bpy) complexes. In a first approach functionalized arylzinc species are prepared in DMF as solvent by electrolytic reduction of the corresponding aryl-bromides or -chlorides in the presence of ZnBr2 and Ni(II)-bpy complexes and then coupled with 2-chloropyridine. In a second approach the cross-coupling occurs from the electrochemical reduction of a stoichiometric mixture of an aryl halide and 2-halopyridine in DMF in the presence of NiBr2bpy as catalyst.

There are described compounds of formula I*, STR1 wherein R. sub.1 is lower alkoxycarbonyl,R 2 is secondary or tertiary lower alkyl or lower alkylthio-lower alkyl, R. sub.3 is phenyl that is unsubstituted or substituted by one or more lower alkoxy radicals, or C 4-C 8 cycloalkyl,R. sub.4 is phenyl or cyclohexyl each substituted in the 4-position by unsaturated heterocyclyl that is bonded by way of a ring carbon atom, has from 5 to 8 ring atoms, contains from 1 to 4 hetero atoms selected from nitrogen, oxygen, sulfur, sulfinyl (--SO--) and sulfonyl (--SO 2--) and is unsubstituted or substituted by lower alkyl or by phenyl-lower alkyl,R 5, independently of R 2, has one of the meanings mentioned for R 2, andR 6, independently of R. sub.1, is lower alkoxycarbonyl,or salts thereof, provided that at least one salt-forming group is present. The compounds are inhibitors of retroviral aspartate protease and can be used, for example, in the treatment of AIDS. They exhibit outstanding pharmacodynamic properties.

A tandem palladium-catalyzed cross-coupling reaction between a pyridyl triflate 1a and a variety of aryl bromides mediated by hexamethylditin is described. The reaction apparently proceeds via the intermediacy of the labile pyridylstannane 1b indicating that the oxidative addition of palladium(0) to the triflate, subsequent transmetalation with hexamethylditin and reductive elimination occurs selectively in the presence of the aryl halide.