A new route to fullerene substituted phenylalanine derivatives

A series of fullerene substituted phenylalanine derivatives have been prepared by the condensation of 1,2-(4'-oxocyclohexano)fullerene with ester or Boc protected (4-amino)phenylalanine, H(2)NC(6)H(4)CH(2)CH(COR(1))(NHCOR(2))(where R(1) = OMe, R(2) = Me; R(1) = OH, R(2) = Me, O(t)Bu). Conversion of the imine to the corresponding amine is achieved by di-acid catalyzed hydroboration. Reaction of the N-Ac amino ester with BBr(3) led to the formation of the parent amino acid, while the Boc-protected derivative readily undergoes coupling with NH(2)-Gly-OEt. The reduction of the imine is not accompanied by hydroboration of the fullerene cage.     

A new synthetic route to phomoidride B and its derivatives

We have developed a new synthetic route to phomoidride B, which could also be applied to the synthesis of phomoidride B derivatives using Pd-catalyzed coupling reaction of a thiolester with an organozinc reagent. In addition, direct construction of the maleic anhydride moiety has been achieved by a Pd-catalyzed carbonylation reaction.     

A new,simple, one-pot route for the synthesis of azocine derivatives

A novel, simple, one-pot procedure for the synthesis of new 7H-naphtho[1,8-ef]pyrimido[4,5-b]azocine-7,10,12,13(8H,9H,11H)-tetraones by the addition reaction of acenaphthoquinone and 6-aminouracil derivatives followed by oxidative cleavage of the corresponding intermediate product in the presence of lead(IV) acetate is reported. Clean reactions, excellent yields, and mild conditions are the main features of this method. The structural assignments are supported by ¹H NMR, ¹³C NMR, and X-ray crystallography data.     

An efficient one-pot route to symmetrically and unsymmetrically substituted 1,4,7-triazacyclononanes also results in the isolation of a stable macrocyclic aminal

A one-pot methodology has been developed for the direct synthesis of symmetrically and unsymmetrically N-substituted derivatives of 1,4,7-triazacyclononane. In the course of these studies the unexpected eight-membered cyclic aminal 7 has been isolated via an acid-catalysed rearrangement of enamine 5.     

A new and general route to 2-pyrrolylglycine, 2-pyrrolylalanine and homo-2-pyrrolylalanine derivatives

A general route to α-, β- and γ-pyrrole-branched α-amino acid derivatives has been developed, which featured a one-pot ring-closing metathesis and aromatization reaction as the key step.     

A new route to 2'-O-alkyl-2-thiouridine derivatives via 4-O-protection of the uracil base and hybridization properties of oligonucleotides incorporating these modified nucleoside derivatives

Oligonucleotides containing 2-thiouridine (s2U) in place of uridine form stable RNA duplexes with complementary RNAs. Particularly, this modified nucleoside has proved to recognize highly selectively adenosine, the genuine partner, without formation of a mismatched base pair with the guanosine counterpart. In this paper, we describe new methods for the synthesis of 2-thiouridine and various 2'-O-alkyl-2-thiouridine derivatives. Oligoribonucleotides having these modified nucleoside derivatives were synthesized, and their hybridization and structural properties were studied in detail by the 1H NMR analysis of these modified nucleosides and Tm experiments of RNA duplexes with their complementary RNA strands.     

Ruthenium-catalyzed annulation of aromatic ketones with internal alkynes: A reliable route to substituted naphthalene derivatives

We report herein the preparation of polysubstituted naphthalene derivatives by the ruthenium-catalyzed benzannulation reaction of aromatic ketones with internal alkynes. This method (1) forms two new carbon-carbon bonds in one single step, (2) accommodates a variety of functional groups, and (3) undergoes mild reaction conditions.     

Synthesis of phenyldithioglyoxalic acid and its esters. A route to a-ketodithioacid derivatives

A novel route has been developed for the direct synthesis of the hitherto unknowna-ketodithioacid. Benzaldehyde has been treated with carbon disulphide in the presence of potassium cyanide, thereby making the intermediate carbanion Ph-C(OH)CN to add on to carbon disulphide eventually leading to thea-ketodithioacid. The methyl and ω-carboxypropyl esters of this acid have also been prepared.     

A new route to the synthesis of ellipticine quinone from isatin

1-(2-Oxo-2-(pyridin-4-yl)ethyl)indoline-2,3-dione can be prepared and converted by treatment with sodium hydroxide into 2-isonicotinoyl-1H-indole-3-carboxylic acid as a key intermediate which can be transformed into ellipticine quinone in a two step sequence.     

A new approach to the synthesis of lysophosphatidylcholines and related derivatives

A new stereospecific synthesis of lysophosphatidylcholines is reported. The sequence relies on orthogonal protection of hydroxyl groups derived from glyceric acid, using fluorenylmethylcarbonate versus tetrahydropyranyl ether functions, that allow regiospecific introduction of substituents to obtain the target phospholipid compound.     

Synthesis and properties of new tetrazines substituted by heteroatoms: towards the world's smallest organic fluorophores

New tetrazines substituted by heteroatoms have been synthesized and their electrochemical and photochemical properties investigated. All compounds are reversibly electroactive with standard potentials shifting cathodically according to the donor character of the substituent. The tetrazine derivatives are also fluorescent with maximum emission wavelengths in the range 550-575 nm. Some of them show very long fluorescence lifetimes (several tens of ns) and remain fluorescent in the solid state without major changes in the spectral features. The fluorescence of one of the derivatives can be efficiently quenched by the presence of electron-rich compounds such as triphenylamines, phenol or anisole, which make them very promising compounds for sensor applications.     

Synthesis, spectral characteristics, and some properties of methylammonium sulfamate monohydrate. A new route to sulfamic acid derivatives

Redox transformations of the products of reactions of the CH₃C(S)NH₂-SO₂-H₂O system components yield methylammonium sulfamate monohydrate [CH₃NH₃]⁺[OSO₂NH₂]^? · H₂O and elemental sulfur. The synthesized compound was characterized by IR, ¹H and ¹³C NMR, and mass spectroscopy and some of its properties were studied.     

General route to the total synthesis of sempervirine analogues containing modified E rings, potential cytostatics

Sempervirine analogues 13a–c with different E rings have been obtained via inverse electron demand Diels–Alder reactions of 5-acetyl-3-(methylsulfanyl)-1,2,4-triazine with cyclic enamines (formation of D and E rings) followed by Fischer indole synthesis under microwave irradiation on solid support (formation of A and B rings) and subsequent annulation of indole derivatives 10a–c via a directed metallation route (formation of C rings).     

On the synthesis and functionalisation of the 4-aza-8,12-dioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenium system

The preparative use of the reaction between tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate and excess of an arylamine such as 4-methylaniline or 4-bromoaniline to yield firstly the aryl functionalised acridinium derivatives and then further in situ reaction to yield the desired functionalised triangulenium salts was found to be problematic. A preparative route for the triangulenium salts is presented along with a demonstration of the further derivatisation by standard Suzuki coupling reaction.     

A new route to the synthesis of isoxazoline derivatives from dihydropyran via cycloaddition reaction in ionic liquid

A new approach to the synthesis and 1,3-dipolar cycloadditions of nitrones has been described from 2,3-dihydro-4H-pyran and various hydroxylamines, with electron-deficient alkynes for the synthesis of isoxazoline derivatives. Significant rate acceleration and improved yields of exclusively exo isoxazolines in 1-butyl-3-methylimidazolium based ionic liquids have been observed. Novel isoxazolines may be used as a precursor for the synthesis of variety of peptides.     

Synthesis, electropolymerization and electrochemical characterization of some new acrylate substituted thiophene derivatives

In this work, three new acrylate substituted thiophene monomers, (3-thienyl) methylacrylate, 6-(3-thienyl)methoxy-hexylacrylate and 11-(3-thienyl)methoxy-undecylacrylate were synthesized and electropolymerized. Electrochemical polymerisation by a potential step technique leads to the formation of an electroactive film on a Pt electrode in each case. The polymerization involves evidently only the thiophene ring, as no sign of polyacrylate formation could be detected. The oxidation of each polymer was studied by in situ external reflectance FTIR spectroscopy, which showed several bands assigned to (bi)polaron type charge carriers in the region 1500–1000 cm⁻¹. The evolution of the conductivity was studied in situ by the contact electric resistance technique. The conductivity of poly(3-thienyl methacrylate) was found to be higher in aqueous solutions than in acetonitrile. The surface of poly((3-thienyl) methacrylate) was found to have a granular structure observed for many polythiophenes, as studied by atomic force microscopy (AFM).     

A convenient and efficient one pot synthesis of unsymmetrically substituted p-terphenyls via a phosphine-free double Suzuki cross-coupling protocol using 1,4-dibromo-2-nitrobenzene as the substrate

A synthetic procedure has been developed to enable the sequential regio-selective Suzuki-Miyaura cross-coupling of 1,4-dibromo-2-nitrobenzene with a variety of arylboronic acids. The first Suzuki coupling step, using a phosphine-free palladium catalyst at room temperature, gave selective coupling at the position ortho to the nitro group, opening a convenient synthetic route to unsymmetrical para-terphenyls. The bromobiaryl product was then subjected directly to the second coupling step, in situ, using preferred aryl-boronic acids to give by this one-pot batch procedure unsymmetrically substituted para-terphenyls in excellent overall isolated yields. This methodology should be particularly suited for the generation of targeted chemical libraries, as well as for the synthesis of precursors of biologically active compounds or natural products which are derived from the unsymmetrical para-terphenyl core.