The first single-crystal diffraction studies on methane, propane, methane/propane, and adamantane gas hydrates SI, SII, and SH have been performed. To circumvent the problem of very slow crystal growth, a novel technique of in situ cocrystallization of gases and liquids resulting in oligocrystalline material in a capillary has been developed. With special data treatment, termed oligo diffractometry, structural data of the gas hydrates of methane, acetylene, propane, a propane/ethanol/methane-mixture and an adamantane/methane-mixture were obtained. Cell parameters are in accord with reported values. Host network and guest are subject to extensive disorder, reducing the reliability of structural information. It was found that most cages are fully occupied by a guest molecule with the exception of the dodecahedral cage in the acetylene hydrate which is only filled to 60%. For adamantane in the icosahedral cage a disordered model is proposed.

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Different phases: Molecular complexes of acetylene and acetone or DMSO are formed simultaneously in different phases. Crystalline acetylene:actone 1:2 (A) and 1:1 (B), as well as acetylene:DMSO 2:1 (C) complexes have been obtained by in situ cocrystallization under pressure in a capillary with the use of an IR laser. The crystal structures may be interpreted as a “frozen” situation of the liquids.

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Total syntheses for four acorane sesquiterpenes, 0-acoradiene (4), -acoradiene (5), and the enantiomers (27 and 28) of acorone (1) and isoacorone (2), are described. The synthetic route involves conversion of (fi)-pulegone (11) into 3-methyl-2-carbethoxycyclopentanone (8) by improvement of literature procedures, then conversion of this into (fi)-3-methyl-2-methylenecyclopentanone (17) by the sequence ketalization, reduction, deketalization, and dehydration, A Diels-Alder reaction between 17 and isoprene gave four adducts 18-21. The para:meta ratio in this reaction was improved from 2:1 to 24:1 by the use of SnCl4 catalysis, which gave a ratio of products of 69: 27:3:1. Structures were assigned to the various isomers on the basis of the known steric and electronic requirements in the Diels-Alder reaction. The major ketones 18 and 19 were purified by preparative high-pressure liquid chromatography. Treatment of 18 with isopropyllithium and then SOCI2 gave -acoradiene (4) and its endocyclic isomer 23, whereas 19 led to -acoradiene (5) and its isomer 25. Hydroboration of 25 followed by Jones oxidation gave an equilibrium mixture of (-)-acorone ( 27), the enantiomer of natural acorone (1), and (+)-isoacorone ( 28), the enantiomer of natural isoacorone (2).Acorone (1), isolated from the oil of Sweet Flag, Acorus calamus L., is the best known member of a small group of spirocyclic sesquiterpenes having the acorane skeleton.3 Other members include isoacorone (2), cryptoacorone (3), and acorenone from the same source,3 as well as acorenone B from Bothriochoa intermedia,4, two unnamed dienes from Vetiveria zizanoides,4 5 and -acorenol, /3-acorenol, aacoradiene, /3-acoradiene, -acoradiene (4), and -acoradiene (5) from Juniperus rígida.5 -Alaskene, isolated from alaska cedar, Chamecyparis nootkatensis, was shown to be identical with -acoradiene, but /3-alaskene from the same source was shown to be enantiomeric to -acoradiene.6 4 5