Romano Grandi

Curcuminoids as potential new iron-chelating agents: spectroscopic, polarographic and potentiometric study on their Fe(III) complexing ability

The pKa values of curcumin and diacetylcurcumin are, here doubtless, determined by means of spectroscopic and potentiometric measurements, and the enolic proton is the more acidic one. The interaction of Fe 3 + with curcumin and diacetylcurcumin, in water/methanol 1:1 solution, leads to the formation of the complex species [FeH2CU(OH)2] and [FeDCU(OH)2 ]( H 2CU and DCU=curcumin or diacetylcurcumin monoanion, respectively) which prevails near pH 7. At more basic condition the prevailing species are [FeH2CU(OH)3] − and [FeDCU(OH)3] − , which prevent metal hydroxide precipitation. 1 H NMR data state that the dissociated -diketo moiety of the ligands is involved in metal chelation. The pKa value of the deprotonation reaction is strongly anticipated by the metal ion, as shown by UV spectral data. The stability constants, evaluated from potentiometric data, are near to that of desferrioxamine, which is, by now, the only iron-chelating agent for clinical use.

Silybin, a new iron-chelating agent

Silybin, a natural occurring flavolignan isolated from the fruits of Silibum marianum, has been reported to exert antioxidant and free radical scavenging abilities. It was suggested to act also as an iron chelator. The complexation and protonation equilibria of the ferric complex of this compound have been studied by potentiometric, spectrophotometric and electrochemical techniques. The formation of the complex silybin-Ga(III) in anhydrous DMSO-d6 has been studied by 1H NMR spectroscopy. Mass spectrometry and infrared spectroscopy on silybin-Fe(III) complex confirm all data obtained by 1H NMR spectroscopy. The experimental results show that silybin binds Fe(III) even at acidic pH. Different ternary complexes were observed at increasing methoxide ion concentration and their stability constants have been calculated. The results show the possible role of silybin in relation to the chelation therapy of chronic iron overload, as occurs in the treatment of Cooleys anemia.

The influence of benzylic protection and allylic substituents on the CuCl-TMEDA catalyzed rearrangement of N-allyl-N-benzyl-2,2-dihaloamides to gamma-lactams. Application to the stereoselective synthesis of pilolactam.

Abstract A number of N-benzylic protecting groups and allylic substituents have been investigated for the rearrangement, promoted by CuCl-TMEDA, of N-allyl-2,2-dihaloamides to 3,4-disubstituted γ-lactams. An appreciable chiral induction was observed at the C-4 site when α-phenylethylamine was used as a chiral protecting group, while an unexpected Diels-Alder reaction occurred when using a 2-furyl-methyl protection. This rearrangement has been applied to the synthesis of pilolactam, a drug with muscarinic activity.

Biosynthesis of nepetalactone in Nepeta cataria

Abstract Iridodial is a key intermediate in the biosynthesis of nepetalactone. One of the steps on the pathway prior to the lactonization is a hydride shift from C-1 to C-10. 10-Hydroxycitronellol is a far more efficient precursor than the C-2/C-3 unsaturated analogue.

Synthesis of 5-methoxylated 3-pyrrolin-2-ones via the rearrangement of chlorinated pyrrolidin-2-ones

The reaction of N-substituted 4-methyl-2-pyrrolidinones or 4-diethoxyphosphoryl analogues, carrying at least two chlorine atoms between the C(3) and C(6) carbons, with alkaline methoxide in methanol afforded the corresponding 5-methoxylated 3-pyrrolin-2-ones, useful adducts for the preparation of agrochemicals or medicinal compounds.

Sulfoxides from Thioethers and MnO2-HCl

Abstract Treatment of thioethers with manganese(IV)oxide-35% aqueous hydrogen chloride in methanol gives sulfoxides in high yields; sulfones are not produced

Acetal chlorination with MnO2-Trimethylchlorosilane

Abstract α-Chloroacetals are obtained in almost quantitative yields, by treating acetals with MnO 2 -trimethylchlorosilane in CH 3 OH:CH 3 CN (1:1). The halogenation is explained by a ligand-transfer process on an enolether intermediate, mediated by a Mn(IV)-chloride species.

The preparation of beta-hydroxysulfoxides

Abstract . Oxidation of β-hydroxy thioethers with MnO2-aqu. 35%/HCl in methanol gives β-hydroxy sulfoxides in high yields.

Structure ofcatena-(2-amino-1,3,4-thiadiazolium, 2-amino-1,3,4-thiadiazole bis(μ-iodo)-di-iodo-bismuth(III)

Abstract[(C2H4N3S) (C2H3N3S) BiI4]∞; [(HL) (L) BiI4]∞ (L=2-amino-1,3,4-thiadiazole),Mr=919.86. monoclinic, P 1 21/a 1,a=7.622(1),b=18.977(2),c=12.821(1) Å, β=102.77(1)°, finalR=0.033. The crystals consist of HL+ cations, neutral L molecules and polymeric [BiI4]∞− anions built up of edge-sharing [BiI6]3− octahedra, with Bi−I(bridging) distances in the range 3.320(1)−3.057(1) Å and Bi−I(terminal) distances in the range 2.917(1)−2.929(1) Å. The1H and13C spectra in DMSO-d6 solution are used in conjunction with the X-ray structural results to establish the preferred protonation site of the thiadiazole ring.

Monoterpene variation in two Achillea ageratum chemotypes

Abstract Artemisia ketone and artemisia acetate are the main monoterpene components in both the flowers and leaves of A. ageratum growing in central Italy, but are replaced by 1,8-cineole in plants growing in Sardinia (Italy).