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The first binuclear Gd‐complex of the 12‐membered pyridine‐based polyaminocarboxylate macrocyclic ligand PCTA was synthesized by C−C connection of the pyridine units through two different synthetic procedures. A dimeric AAZTA‐ligand was also synthesized with the aim to compare the relaxometric results or the two ditopic Gd‐complexes. Thus, the 1H relaxometric study on [Gd2PCTA2(H2O)4] and on [Gd2AAZTA2(H2O)4]2− highlighted the remarkable rigidity and compactness of the two binuclear complexes, which results in molar relaxivities (per Gd), at 1.5 T and 298 K of ca. 12–12.6 mM−1 s−1 with an increase of ca. 80 % at 1.5 T and 298 K (+70 % at 310 K) with respect to the corresponding mononuclear complexes., Two novel binuclear PCTA2 and AAZTA2 ligands were synthesized with a multistep process. Their GdIII‐complexes results in molecular relaxivities at 1.5 T and 298 K of ca. 24–25 mM−1 s−1 thanks to the rigidity and compactness of the ligands. These values are remarkably higher that those found for the corresponding mononuclear complexes.

The present review is devoted to illustrate the state of the art of the syntheses of indoles, focusing particularly on the most recent developments of new synthetic approaches. Emphasis is given to the preparation of natural products or bioactive compounds containing the indole unit. We present a historical perspective of indole synthesis showing the strategies by choosing the nitrogen precursors. The review is organized sharing the indole synthetic approaches by using different nitrogen-containing functional groups in aromatic substrates used as source of the nitrogen of the indole moiety. Some functional groups and some typical reactions are particularly stressed and highlighted because of the limited coverage given in previous reviews published on this topic. Other synthetic approaches more used and discussed in recent, complete and excellent reviews on the topic are summarized but the most recent published results are highlighted. Our interest is particularly focused on the indolization procedures and on the different methods used for the ring closure and no attention is given to modification of indole structures starting from molecules with a preformed indole unit. Intriguing indole syntheses are continually discovered and the importance that the scientific community gives to these new developments is connected with the strategic role of molecules containing the indole unit. Indoles are the class of heterocycles with more applications and extensive interest due to their biological and pharmacological activity.

The new C 2 -symmetrical 1,2-diamine { N , N ′-bis[(1 R ,2 R ,4 R )-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]-1,2-ethanediamine} 3 has been synthesized from commercial (1 R )-(+)-camphor 1 and scrutinized as ligand in the oxidative biaryl coupling of naphthol derivatives. Under the optimal conditions employing a Cu(I)- 3 triflate complex (10 mol%) in dichloroethane–MeCN and molecular sieves with air as the oxidant, aryl coupling of naphthol derivatives could be achieved in satisfactory yields (48–90% yield) and ees of up to 65%. The ester moiety at the 3-position of the substrate was found to be crucial for a satisfactory asymmetric induction in the present coupling reaction.

A practical preparation of the versatile macrocycle 1,4,7,10-tetraazacyclododecane (cyclen) was developed starting from cheap and easily available starting materials as ethylenediamine and glyoxal.

A novel heptacoordinating ligand consisting of a thirteen-membered tetraazamacrocycle containing the pyridine ring and bearing three methylenephosphonate groups (PCTP-[13]) has been synthesized. Its Gd(III) complex displays a remarkably high longitudinal water proton relaxivity (7.7 mM–1 s–1 at 25 °C, 20 MHz and pH 7.5) which has been accounted for in terms of contributions arising from (1) one water molecule bound to the metal ion, (2) hydrogen-bonded water molecules in the second coordination sphere, or (3) water molecules diffusing near the paramagnetic chelate. Variable-temperature 17O-NMR transverse relaxation data indicate that the residence lifetime of the metal-bound water molecule is very short (8.0 ns at 25 °C) with respect to the Gd(III) complexes currently considered as contrast agents for magnetic resonance imaging. Furthermore, GdPCTP-[13] interacts with human serum albumin (HSA), likely through electrostatic forces. By comparing water proton relaxivity data for the GdPCTP-[13]-HSA adduct, measured as a function of temperature and magnetic field strength, with those for the analogous adduct with GdDOTP (a twelve-membered tetraaza macrocyclic tetramethylenephosphonate complex lacking a metal-bound water molecule), it has been possible to propose a general picture accounting for the main determinants of the relaxation enhancement observed when a paramagnetic Gd(III) complex is bound to HSA. Basically, the relaxation enhancement in these systems arises from (1) water molecules in the hydration shell of the macromolecule and protein exchangeable protons which lie close to the interaction site of the paramagnetic complex and (2) the metal bound water molecule(s). As far as the latter contribution is concerned, the interaction with the protein causes an elongation of the residence lifetime of the metal-bound water molecule, which limits, to some extent, the potential relaxivity enhancement expected upon the binding of the paramagnetic complex to HSA.

The eight-membered 3,7-dihydroxy-3,7-dioxoperhydro-1,5,3,7-diazadiphosphocine-1,5-diacetic acid was obtained with a one-step reaction of glycine, formaldehyde and hypophosphorous acid in acidic aqueous medium. A preliminary investigation of its coordination properties is reported.

The alkylation of the chiral Schiff base derived from the condensation of (+)-ketopinic acid and diethyl aminomethylphosphonate followed by hydrolysis affords diethyl (S)-α-amino-α-alkyl phosphonates with high enantiomeric excesses when benzyl or allyl halides are used in the alkylation step. An improved procedure for the preparation of diethyl aminomethylphosphonate is also reported.

An innovative MRI contrast agent based on the unprecedented and easily obtained ligand AAZTA is described. The simple and straightforward synthesis of the ligand, together with the potentiometric and relaxometric behavior of the corresponding Gd(III) chelate, is reported. The complex [Gd(AAZTA)]- shows outstanding magnetic properties connected with high thermodynamic stability in aqueous solution and a nearly complete inertness toward the influence of bidentate endogenous anions, placing this compound as one of the most promising candidates for the development of high performance MRI contrast agents.

Reactions of aliphatic branched aldehydes with proline in dimethyl sulfoxide or acetonitrile solution afford oxazolidin-5-ones with high diastereoselection. Linear aldehydes afford aldolic/crotonic condensation products; with short reaction times, the presence of Oxazolidinones can be detected in the pmr spectra. Acyclic aminoacids and branched aldehydes yield a reaction mixture the pmr and ir spectra of which give evidence for iminic-oxazolidinone equilibria. The structure of (2R,5S)-2-trichloromethyl-1-aza-3-oxabiciclo-[3.3.0]octan-4-one has been confirmed by X-ray diffraction analysis.

A new entry to the drimane-related sesquiterpene Confertifolin is reported. The key step involves the conversion of a β-phenylthio-α, β-unsaturated ketone into the corresponding silylcyanohydrin followed by diisobutylaluminum hydride reduction to the homologous α,β-unsaturated aldehyde.

(1989). A CONVENIENT PREPARATION OF ETIWL 7-BROMOHEPTANOATE. Organic Preparations and Procedures International: Vol. 21, No. 2, pp. 253-254.