Single-molecule surface-enhanced Raman scattering: Current status and future perspective

The single-molecule surface-enhanced Raman scattering （smSERS） has been extensively studied after the initial observation in 1997, yet there still exist unsettled issues in the fundamental mechanism of smSERS. In this review, we survey some of the recent breakthroughs in the mechanism of smSERS and its application.     

Magnetic resonance imaging features in melanoma

T1 and T2 relaxation time shortening secondary to paramagnetic compounds has been described in melanoma. The purpose of this paper is to evaluate the signal behavior of melanoma involved in various body areas using short TR, TE and long TR, TE sequences. Twenty-seven sites of melanoma were evaluated with MR using T1 weighted and T2-weighted techniques. Using fat and muscle signal intensities as references tissues, lesions were graded into high, low or intermediate intensity categories for each of the sequences. Four signal patterns emerged. The typical pattern characterized by high signal on T1-weighted images and low signal on T2-weighted images reflected T1 and T2 shortening. The other pattern categories comprised of lesions demonstrating low signal T1-weighted images and high signal on T2-weighted images, high signal on both T1- and T2-weighted images and lesions showing intermediate signal on either T1- or T2-weighted images. We observed a tendency away from the typical signal pattern in extraocular melanoma cases with only one of 14 demonstrating this pattern. Moreover, only seven of thirteen ocular melanomas exhibited such behavior. Possible explanations for this findings as well as the existence of a variety of MR appearances to melanoma are offered. We conclude that while signal patterns showing T1 and T2 shortening are typical of melanoma, the absence of these does not exclude the diagnosis.     

The Synthesis of (±)-α-Vetispirene Via the Dieckmann Condensation of Ethyl 4-(2,6-Dimethyl-1-Carbethoxycyclohex-2-Enyl)-Butyrate

A new process for the synthesis of (±)-α-vetispirene ( 1 ) starting from 2,4-dimethyl-3-carbethaxycyclohexene ( 2 ) is described. The key steps include the stereoselective alkylation of 2 with ethyl 4-bromo-butyrate to yield ethyl 4-(2,6-dimethyl-1-carbethoxycyctohex-2-enyl)-bytyrate ( 3 ) and spiroannulation of 3 by Dieckmann condensation to give 2-carbethoxy-6,10-dimethyl spiro[4,5] deca-6-en-1-one ( 4 ).     

Fragmentation of α-Acetoximino Ketoesters in Polyphosphoric Acid

Fragmentations of various α-acetoximino ketoesters in neat polyphosphoric acid medium to form acylium ions were studied. The resulting acylium ions were trapped by benzene rings either intermolecularly or intramolecularly.     

Analysis of pipecolic acid in biological fluids using capillary gas chromatography with electron-capture detection and [2H11]pipecolic acid as internal standard.

A sensitive and accurate stable isotope dilution assay was developed for the measurement of pipecolic acid in body fluids using capillary gas chromatography with electron-capture detection. The method utilizes [2H11]pipecolic acid as the internal standard. Sample preparation consisted of derivatization in aqueous solution (pH 11.5) of the amine moiety with methyl chloroformate to the N-methylcarbamate, followed by acidic ethyl acetate extraction at pH less than or equal to 2 and further derivatization of the carboxyl moiety with pentafluorobenzyl bromide, the excess of which was removed by solid-phase extraction. Control values have been determined in the plasma of at-term infants, age greater than 1 week (n = 21, mean = 1.36 microM, range = 0.47-3.27 microM). The utility of the method was demonstrated by quantitating pipecolic acid in biological fluids derived from patients with peroxisomal disorders. The method was validated against an established electron-capture negative ion mass fragmentographic technique.     

The Decarboxylation and Dimerization Product of 1-Methylindole-3-Fumaric Acid-2,4-Bis-(1-Methylindol-3-YL)-2-Methyl-γ-Butyrolactone-4-Carboxylic Acid

The decarboxylation and dimerization product of 1-methylindole-3-fumaric acid was elucidated as 2, 4-bis-(1-methylindol-3-yl)-2-methyl-γ-butyrolactone-4-carboxylic acid. Some of its derivatives were also prepared.     

Preparation of 3,4,5,3′-Tetramethoxy-4′,5′-Methylenedioxybenzophenone and Bis-(3-Methoxy-4,5-Methylenedioxy)-Benzophenone

The preparation of 3,4,5,3′-tetramethoxy-4′,5′-methylenedioxybenzophenone (I) and bis-(3-methoxy-4,5-methylenedioxy)-benzophenone(II) were reported. The synthesis of these compounds were accomplished using two separate synthetic routes starting from gallic add and its derivatives to the corresponding benzils. Both compound I and II were obtained by benzilic acid rearrangement of the benzils and followed by an oxidative decarboxylation.     

The Reaction of 2-Methylindole with Pyruvic Acid

The reaction of 2-methylindole with pyruvic acid was studied. Two products are found to be depending on experimental conditions, including the 2:2 condensation adduct and the 2:1 condensation adduct. The reaction mechanism evidently involves a 1:1 adduct of 2-hydroxy-2-(2-methylindol-3-yl)-propionic acid as an intermediate.     

The Reaction of Indole Magnesium Bromide with Ketones I. The Reaction of Indole Magnesium Bromide with Cyclohexanone

Indole magnesium bromide, produced by reacting indole with n-butyl magnesium bromide in ether, was reacted with cyclohexanone at ice or room temperature to yield 1-(indol-I-yl)-cyclohexanol (I), which is unstable and may be decomposed easily into indole and cyclohexanone in acidic condition. Indole magnesium bromide reacted with cyclohexanone in refluxing benzene or in anisole at 80°C, to form two products, 1-(indol-3-yl)-cyclohexanol (II) and 1-(indol-3-yl)-cyclohexene (III). (II) could be converted to (III) by heating (II) in phosphoric acid. Reaction of III with maleic anhydride gave a Diels-Alder adduct (IV). Reaction of indole magnesium bromide with cyclohexanone in anisole at 130°C yielded (III) and a trimolecular condensation product of cyclohexanone (V).