Synthese von Cotarnin-Iodid

Summary Starting from 4-methoxy-1,3-benzodioxol-5-carbaldehyde (croweacin aldehyde,3) a six-step synthesis of cotarnin iodide (9, 67% total yield) is described.

     

A molecular mechanics study of neutral molecule complexation with crown ethers

Molecular mechanics methods are applied to the study of neutral molecule complexation with crown ethers. Protocols for the development of parameters necessary to describe these molecule-molecule interactions are presented. Application of these methods to the study of 1:1 and 2:1 (guest:host) complexation between acetonitrile (1), nitromethane (2), malononitrile (3) and dimethylsulfone (4) reveals positive cooperativity in formation of the 2:1 complexes in isolation.     

Fourier transform and CARS spectroscopy of the ν1 and ν3 fundamental bands of 14NH3

The ν₁ and ν₃ fundamental bands of ¹⁴NH₃ have been measured using the techniques of Fourier transform and coherent anti-Stokes Raman spectroscopy. The effective values of the band origins, rotational and centrifugal distortion constants, and parameters of the vibrational-rotational interactions have been obtained by analyzing these bands as essentially regular parallel and perpendicular bands, with the “off-diagonal” local resonance interactions excluded from the fit. The “diagonal” l-type resonance effects have been included into the analysis of the ν₃ band for the +l, K = 1 and ?l, K = 2 levels.     

The ν2 band of 15NH3

High-resolution Fourier transform sepctra of the ν₂ band of ¹⁵NH₃ have been recorded in the region 725–1250 cm^?1 with a precision better than 0.0003 cm^?1. A simultaneous weighted least-squares analysis of these data, together with previously published data, has been carried out, to yield molecular parameters which fit the data within the limits of their experimental accuracies.     

Very high resolution CO laser spectrometer and first sub-Doppler line-shape studies near 60 THz (5 μm)

2 laser standards. Using this technique, we can tune the CO laser frequency with absolute frequency control within the gain profile of each laser transition. The frequency uncertainty is smaller than 15 kHz, corresponding to Δν/ν=2.5×10^-10. Moreover, we obtain a reduction of the CO laser linewidth by a factor of 2 down to 65 kHz, corresponding to a spectral resolution of δν/ν=1×10^-9. With this outstanding accuracy and resolution we studied the shape of saturation dips in rovibrational lines of CO and carbonyl sulfide (OCS) at low pressure (<5 Pa). The self-pressure-broadening rate of CO was found to be γ_c=+83(7) kHz/Pa in this pressure region. This value is about four times higher than values resulting from previous measurements at much higher pressures. To our knowledge the measurements described here are the first line-shape studies with sub-Doppler resolution in the 5 μm spectral region. Received: 4 November 1996     

Preparation of enantiomerically pure 5,6-dihydroxy-isobenzofuranones and 5,6-dihydroxy-4,7-methano-isobenzofuranones

Summary Optically pure available lactones1 and5 were diastereoselectively oxidised tocis-diols2 and6 by KMnO₄ and to epoxides3 and7 by 3-chloroperoxybenzoic acid. Epoxide3 was cleaved totrans-diol4, whereas hydrolysis of7 afforded tricyclic carboxylic acid8. Optic ally puredihydroxylactones2,4, and6 are valuable models for structure determination of the antimicrobial garlic component garlicin.

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Synthese enantiomerenreiner 5,6-Dihydroxy-isobenzofuranone und 5,6-Dihydroxy-4,7-methano-isobenzofuranone

Zusammenfassung Die in enatiomerenreiner Form verfügbaren Lactone1 und5 wurden durch diastereoselektive Oxidation mit KMnO₄ zu dencis-Diolen2 und6 bzw. mit 3-Chlorperoxybenzoesäure zu den Epoxiden3 und7 umgesetzt. Das Epoxid3 liefert bei der Hydrolyse dastrans-Diol4, während aus7 die tricyclische Carbonsäure8 entsteht. Die optisch reinen Dihydroxylactone2,4 und6 können als Vergleichssubstanzen zur Strukturaufklärung des antimikrobiellen Knoblauchinhaltsstoffes Garlicin dienen.

     

Simultaneous two-line operation of a CW CO laser with arbitrary choice of laser transitions

An experimental scheme is discussed, by which we can operate a CO laser at two individually selectable lines from the same gain tube. There are virtually no restrictions on the wavelength separation of the two lines within the manifold of the available lasing transitions. Experimental verifications of this scheme are described and the mutual influence of the simultaneous laser operation is discussed.Dedicated to Professor Siegfried Penselin on the occasion of his 60th birthday     

A Faraday Laser Magnetic Resonance spectrometer for spectroscopy of molecular radical ions

We describe a mid-infrared Laser Magnetic Resonance (LMR) spectrometer which is based on a cryomagnet and a sealed-off CO-laser. Faraday rotation combined with a multireflection cell is used for polarization sensitive detection of molecular radical ions. Experimental details and first spectroscopic examples are given.     

Optically stabilized tunable diode-laser system for saturation spectroscopy

We present an optically stabilized lead-salt diode-laser system which is the nucleus of a very-high-resolution instrument for sub-Doppler molecular spectroscopy in the mid-infrared. By application of external optical feedback, we have narrowed the diode-laser linewidth by two orders of magnitude, yielding a spectral width of less than 200 kHz. The diode- laser frequency is stabilized and controlled via the external reflector by variable-frequency offset-locking the diode-laser to a CO laser frequency. This substantial improvement in the spectral properties enabled us to perform a Lamb-dip experiment on a carbonyl sulfide (OCS) absorption line near 1985 cm^–1. We were able to detect a saturated dispersion signal at low pressure (5 Pa) with a signal-to-noise ratio of several thousand. The present paper describes the unique features of the optically stabilized tunable diode-laser system and its use as a spectroscopic tool for sub-Doppler applications.