A Total Synthesis of Aphidicolin: Stereospecific Synthesis of (±)-3α, 18-Dihydoxy-17-Noraphidicolan-16-one

A simple, efficient, and stereospecific total synthesis of (±)-3α, 18-dihydroxy-17-noraphidicolan-16-one (2) , by solvolytic rearrangement of the endo-bicyclo-[2.2.2]oct-5-en-2-yl methanesulfonate 16 , is described. Since aphidicolin (1) has already been obtained from 2 , the preparation of the latter formally constitutes a new total synthesis of 1 .     

Reaction of 2-dimethylaminomethylene-1,3-diones with dinucleophiles. III. Synthesis of 5-acylpyrimidines and 7,8-dihydroquinazolin-5(6H)-ones

The reaction of open-chain and cyclohexane sym-2-dimethylaminomethylene-1,3-diones with amidines and guanidine in refluxing ethanol gave, generally in good yields, a series of 5-acylpyrimidines and 7,8-dihydroquinazolin-5(6H)-ones, respectively. With formamidine (and in part acetamidine), 2-formylimino-1,3-diones were formed in general, as sole products or mixtures with the corresponding pyrimidines or dihydroquinazolinones.     

Ambient pressure synthesis of corundum-type IN2O3

This communication reports the formation of the high-pressure modification of indium (III) oxide (so-called corundum-type or hexagonal In2O3) under ambient pressure. Corundum-type In2O3 was obtained by precipitation from the solution of indium nitrate in methanol by adding concentrated ammonia solution and subsequent calcination of the obtained precipitate at 250-500 degrees C. The role of the impurities and the additives in the stabilization of corundum-type In2O3 is discussed.     

High energy collisional spectroscopy of [RCOO]− anions from negative ion chemical ionization of fatty acid methyl esters

Saturated and mono-unsaturated fatty acid methyl esters as well as corresponding underivatized acids gave abundant carboxylate anions [RCOO]^? under negative ion chemical ionization (OH^? and NH₂ ^?) and electron attachment conditions. B/E or mass-analysed ion kinetic energy spectra of fragments arising from high energy collision activated dissociation (CAD) of these [RCOO]^? species contained decisive information on the original structure of the neutrals. From an analytical point of view, the method can utilize the gas chromatographic mass spectrometric combination and, in the B/E mode, can be used in practice on any double-focusing mass spectrometer.     

Reaction of 2-dimethylaminomethylene-1,3-diones with dinucleophiles. VIII. Synthesis of ethyl and methyl 2,4-disubstituted 5-pyrimidinecarboxylates

Reaction of ethyl or methyl 2-dimethylaminomethylene-3-oxoalkanoates with N-C-N dinucleophiles such as guanidine, acetamidine or benzamidine afforded in high yields the relative esters of 4-substituted 2-amino-, 2-methyl- or 2-phenyl-5-pyrimidinecarboxylic acids, respectively. These esters were hydrolyzed to the corresponding carboxylic acids, which were converted by heating to 4-substituted 2-pyrimidinamines, 2-methyl or 2-phenylpyrimidines, respectively, generally in excellent yields. The 4-unsubstituted ethyl 2-amino-, 2-methyl- and 2-phenyl-5-pyrimidinecarboxylates were obtained in moderate yields by reaction of the above dinucleophiles with ethyl 2,2-diformylacetate. These esters were hydrolyzed and the corresponding acids (with the exception of the 2-methyl derivative) were decarboxylated to give 2-pyrimidinamine and 2-phenylpyrimidine in satisfactory yields.     

Efficient 3D database screening for novel HIV-1 IN inhibitors

We describe the use of pharmacophore modeling as an efficient tool in the discovery of novel HIV-1 integrase (IN) inhibitors. A three-dimensional hypothetical model for the binding of diketo acid analogues to the enzyme was built by means of the Catalyst program. Using these models as a query for virtual screening, we found several compounds that contain the specified 3D patterns of chemical functions. Biological testing shows that our strategy was successful in searching for new structural leads as HIV-1 IN inhibitors.     

Electron impact mass spectrometry of hemiterpenoid tricyclic quinoline alkaloids

The mass spectral behaviour of some quinoline-type alkaloids, 3,4-dihydro-2H,5H-pyrano[3,2-c]quinolin-5-ones, isomeric 3,4-dihydro-2H,5H-pyrano[2,3-b]quinolin-5-ones and 2H,5H-pyrano[3,2-c]quinolin-5-ones, was studied in detail with the aid of linked scans, exact mass measurements and collisional spectrometry. The occurrence of a partial isomerization of the differently annulated isomers to a common, open-chain structure is discussed.     

Electron impact mass spectrometry of 2-(methoxycarbonylmethyl)-2-phenyl-1,3-benzoxathiole and 2-acetonyl-2-phenyl-1,3-benzoxathiole

The electron impact mass spectrometric behaviour of 2-(methoxycarbonylmethyl)-2-phenyl-1,3-benzoxa-thiole 3a and 2-acetonyl-2-phenyl-1,3-benzoxathiole 3b has been studied in detail. The structures of the more interesting fragment ions have been confirmed with the aid of accurate mass measurements, linked scans and collisional activation experiments. In addition to the ionic species already described in the general fragmentation pattern of 1,3-benzoxathiole derivatives, other fragments arising from the interaction of the carboxy-containing chain with the sulfur atom of these compounds have been observed and evidence presented.     

Pyrolytic behaviour of metal containing compounds in oxygen determination with elemental analyzer

Summary The oxygen determination in organic compounds containing metals with elemental analyzer has been reinvestigated by studying the behaviour during the pyrolytic process, with particular attention to the formation and decomposition of oxides. In order to obtain more satisfactory analytical results the use of particular additives has been examined. The determinations have been performed with a Perkin-Elmer Elemental Analyzer Model 240, by using 50% platinized carbon at 950° C, and with a Carlo Erba Elemental Analyzer Model 1106, by using nickelized carbon at 1050° C.

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Über das pyrolytische Verhalten metallhältiger Verbindungen bei der Sauerstoffbestimmung

Zusammenfassung Die Sauerstoffbestimmung in metallhältigen organischen Verbindungen wurde neuerlich untersucht, besonders hinsichtlich des Pyrolysevorgangs und der dabei stattfindenden Bildung und Zersetzung von Oxiden. Zwecks Erzielung besserer Ergebnisse wurden besondere Zusätze zur Einwaage versucht. Die Bestimmungen wurden mit einem Elemental-Analyzer, Modell 240, von Perkin-Elmer mit 50% platiniertem Kohlenstoff bei 950° C und mit einem Elemental-Analyzer, Modell 1106, von Carlo Erba unter Verwendung von nickelhaltigem Kohlenstoff bei 1050°C ausgeführt.

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Presented at the 9th International Symposium on Microchemical Techniques, Amsterdam, August 28–September 2, 1983.     

On the detailed mechanisms of collision-induced dissociation experiments performed by electrospray ion trap

The product ion spectra obtained by electrospray ionization (ESI) ion trap instruments exhibit a higher number of fragment ions than those achieved by other ion-trap-based systems, indicating the presence of more effective energy deposition mechanisms. This behavior can be attributed to several different reasons, among which different initial internal energy of the precursor ions, pre-activation due to collisions taking place outside the trap, different target gas mixtures inside the trap, and different ion trap geometry were considered. Data obtained from experiments using a triple quadrupole instrument, CI-ion trap, and ESI-ion trap have been compared. The results so achieved seem to indicate that the presence inside the trap of neutral molecules of the solvent employed for the ESI process have a relevant role, promoting high energy deposition in the colliding ions.