Arturo Battaglia

High-performance liquid chromatographic analysis of physiological amino acids in human brain tumors by pre-column derivatization with phenylisothiocyanate

A reversed-phase high-performance liquid chromatographic technique for the determination of free amino acids in five biopsies of human brain tumors (two meningiomas, one glioblastoma and two oligodendrogliomas) is described. The frozen tissues were homogenized, deproteinized with perchloric acid and neutralized with potassium hydroxide. Aliquots of the supernatant containing the physiological amino acids are used for pre-column derivatization with phenylisothiocyanate. The derivatized PTC-amino acids (phenylthiocarbamyl derivatives) are stable for a five day period if stored as a powder at -20 degrees C in an inert atmosphere and they can be analyzed on a reversed-phase column (PicoTag) using a gradient of two eluents with absorption detection at a wavelength of 254 nm. Good resolution of several amino acids (>30) is achieved within ca. 60 min. For most amino acids this method is suitable for an accurate measurement over a wide range of physiological concentrations (50-400 pmol) starting from a very small amount of sample.

Biological Properties of IDN5174, a New Synthetic Camptothecin with the Open Lactone Ring

A series of water-soluble camptothecins obtained by linking a spermidine moiety to the 21-position of the open form through an amidic bond have been tested for their biochemical and biological activities. Growth inhibition assay on the human non-small cell lung cancer carcinoma NCI-H460 cell line revealed that the camptothecin analogues were less potent than topotecan and SN38 after 1 hour of treatment. The potency increased after 72 hours of exposure, being similar to that of reference camptothecins. The analysis of topoisomerase I-mediated DNA cleavage using the purified enzyme indicated that the novel camptothecin analogues retained ability to poison topoisomerase I and displayed the same cleavage pattern of SN38. Persistence of the DNA cleavage was comparable with that of SN38. Stabilization of the cleavable complex was not the result of hydrolysis of the N-C bond between polyamine and the drug because no free camptothecin was recovered at the end of DNA cleavage in presence of IDN5174, the analogue selected for detailed studies. IDN5174 exhibited an antitumor activity comparable with that of topotecan and irinotecan against NCI-H460 tumor xenograft. The pharmacokinetics in mice showed a favorable disposition in tumor tissue with low amount of camptothecin detectable in plasma and tumor (around 5-10%), thus supporting the efficacy of intact IDN5174. In conclusion, we found that IDN5174 maintained the biological and antitumor properties, in spite of lack of the closed E ring. The available results support the interpretation that the polyamine linked at the 21-position may allow a favorable drug interaction in the ternary complex.

Cyclocondensation reactions of optically active α-alkoxy aldehydes to ketene imines: Synthesis of chiral 2-iminooxetanes

Abstract The Lewis acid promoted hetero-cycloaddition of a series of ketene imines to stereogenic ( S )-α-alkoxy aldehydes is regiospecific and gives diastereomeric mixtures of the corresponding optically active 2-iminooxetanes. The possibility of achieving a “chelation” or “non-chelation” controlled facial selectivity is investigated. The non-chelating Lewis acids (BF 3 .Et 2 O and ZnCl 2 .Et 2 O) govern the selectivity of the cycloaddition, anti -Cram products being preferentially formed whith low and medium size ketene imines. In contrast, syn -Cram configured isomers are preferentially formed within the sterically demanding tert -butylketene N - p -methoxyphenylimine in the presence of catalytic amounts of lanthanide catalysts.

Synthesis and HSA binding characterisation of the water soluble 7-succinylpaclitaxel.

A water soluble paclitaxel analogue, the 7-hemisuccinylpaclitaxel, was synthesised and its binding to human serum albumin (HSA) was characterised by difference circular dichroism and optical biosensor methodologies. The carboxylate group was introduced at paclitaxel C-7 position to improve the drug water solubility without significantly changing the biological activity. The paclitaxel analogue showed a relatively low affinity to HSA (3.5x10(4) M(-1)), while no significant interactions were evidenced with selective markers for the most characterised binding sites on the carrier, suggesting a non-selective binding to low affinity binding sites.

Synthesis and desilylation of (2R,3S)-α-methyl-α-silyl-α,β-2,3-dihydroxycarboxylic methyl esters

Abstract Addition reactions of the chiral lithium (2 S )-enolates of the (2 S ,5 S )-2- tert -butyl-5-methyl-[1,3]dioxolan-4-one and (2 S ,5 S )-2- tert -butyl-2,5-dimethyl-[1,3]dioxolan-4-one with linear aliphatic acylsilanes yield the corresponding (2 S ,5 R ,1′ R )-1′-trimethylsilyl-dioxolanone alcohols. Sodium methoxide-induced removal of the acetal center at C-2 affords the corresponding methyl (2 R ,3 R )-2,3-dihydroxy-2-methyl-3-trimethylsilyl alkanoates. The desilylation of these esters occurs with complete retention of configuration yielding the corresponding (2 R ,3 S )-2,3-dihydroxy-2-methyl-alkanoic acids.

Synthesis and chemical behaviour of thioacylsilanes (silyl thioketones). Part 1. Oxidation to S-oxides, conversion into silylated thiiranes, silylated triarylethylenes, and α-silylated sulphides

Trimethylsilyl and triphenylsilylaryl thioketones have been synthesized by acid catalysed reaction of the corresponding ketones with hydrogen sulphide. Such silylated thioketones have been oxidized to give S-oxides and converted with diaryldiazomethanes into triaryl thiiranes; upon treatment with organolithium nucleophiles they undergo thiophilic addition. The ready desulphurization with triphenylphosphine of silylated thiirans to the corresponding silyl triaryl ethylenes is also reported.

Cycloaddition reaction of heterocumulenes and ester enolates: A novel synthesis of 4-alkylidene-azetidin-2-ones.

Abstract The cycloaddition of ketenimines with ester enolates gives 4-alkylidene-azetidin-2-ones in fairly good yields.

Assessment of the absolute configuration of a series of (3R)-3-hydroxy-3-alkyl-β-lactams

Abstract The absolute stereochemistry of a series of (3R)-3-hydroxy-3-alkyl-β-lactams has been determined by circular dichroism and NMR spectroscopies. The sign of the circular dichroism band between 250 and 220 nm was related to the stereochemistry by applying the β-lactam sector rule. The NMR analysis unambiguously determines the relative configuration at C3 and C4 of the β-lactam ring. The reliability of the method has been proved by X-ray analysis of two of the examined compounds. The obtained results are in agreement with the mechanism proposed for the employed synthetic route.

Photoelectron spectra of nitrones and nitrile oxides

Abstract The photoelectron spectra of five nitrones—N- t -butyl-, C-phenyl-N-methyl-, C-phenyl-N- t -butyl-, C-mesityl-N-methyl-nitrone and dihydroisoquin

Chemistry of silyl thioketones. Part 3. Cycloaddition reactions with heterodienes (α-nitrosostyrene and ketene imines)

Silylated heterocycles viz: 4H-1,5,2-oxathiazines (4a, b), 4H-3,1 -benzothiazines (8), (9), 5,6-dihydro-2H-thiopyrans (11a, b), were obtained in reactions of silyl thioketones (1a, b) with α-nitrosostyrene (2), dimethylketene N-p-tolylimine (3a), and methylvinylketene N-p-tolylimine (3b) respectively.In the reaction of (1a, b) with (3b), in which a heterodiene and a homodiene system is present, a variation in the periselectivity is found with respect to diaryl thioketones. Desilylation of trimethylsilyl adducts was also investigated. In the case of (4a), desilylation affords α-aminostyryl benzoyl sulphide (5) whereas the adducts (9) and (11a) give, in good yield, the corresponding hydrogen-substituted heterocycles (10) and (12) respectively.