Inhaltsstoffe des Osmanthus-Absolues. 4. Mitteilung: Megastigma-5, 7 (E), 9-trien-4-on und Megastigma-5, 8 (E)-dien-4-on

Constituents of Osmanthus Absolute, 4th Communication. Megastigma-5, 7 (E), 9-triene-4-one and Megastigma-5, 8 (E)-diene-4-one In continuation of our communications on constituents of Osmanthus absolute, we now report on the occurrence of the two title compounds 1 and 2a in this natural substrate (0.01-0.02% each). Their structures were confirmed by synthesis starting from β-ionone via the common intermediate 4-oxo-β-ionol ( 9 ). Some further minor components bearing corresponding structural features are tabulated in view of possible biogenetic pathways leading to 1 or 2a , respectively. In order to clarify the olfactory behaviour, we also synthesized some analogous derivatives in the irone series, these substances being not yet found in nature.     

Semiempirical calculations of ground state properties and rotational barriers in conjugated ethylenes

Ground state properties of methyl-2-carbomethoxy-3-dimethylaminoacrylate 4, and methyl-2-carbomethoxy-3-(1-aziridino) acrylate 5 were calculated by semiempirical methods and found to be in good agreement with the experiment. Barriers to rotation about the CC double bond and the C-N single bond were also calculated, allowing for structure relaxation in the transition state. A comparison of the calculated and experimental barriers to rotation shows good agreement for the rotation about the C-N bond and poor agreement for the rotation about the CC bond. This discrepancy is explained in terms of solvent stabilization of the polar transition state.     

The photosensitized rearrangement of aryl-substituted tricyclo[2.2.0.02,6]hexanes to bicyclo[3.1.0]hex-2-enes

The triplet sensitized irradiation of 3-allyl-diaryl-substituted cyclopropenes to bicyclo[3.1.0]hex-2-enes proceeds via an intramolecular [2+2]-cycloaddition followed by a subsequent rearrangement of the initially formed tricyclo[2.2.0.0^2,6]hexane skeleton.     

Functions defining capillary structure of microporous adsorbents

The applicability of earlier derived equations for adsorption isotherms for the determination of differential curves characterizing the approximate distribution of micropore volumes in relation to their radii is studied. It is concluded that besides the Gaussian distribution, the Rayleigh and exponential distributions also possess a physical sense.