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ent-Kaurene is a tetracyclic diterpene hydrocarbon and a biosynthetic intermediate of the plant hormone gibberellins. In flowering plants, ent-kaurene is biosynthesized from geranylgeranyl diphosphate (GGDP) by two distinct cyclases, ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase (KS). Recently, the moss Physcomitrella patens ent-kaurene biosynthetic gene was cloned and functionally characterized. The bifunctional ent-kaurene synthase [P. patens CPS/KS (PpCPS/KS)] produces both ent-kaurene and 16α-hydroxy-ent-kaurane from GGDP via ent-copalyl diphosphate. Here, we cloned and analyzed the function of a cDNA encoding bifunctional ent-kaurene synthase from the liverwort Jungermannia subulata [J. subulata CPS/KS (JsCPS/KS)]. JsCPS/KS catalyzes the cyclization reaction of GGDP to produce ent-kaurene but not 16α-hydroxy-ent-kaurane, even though the PpCPS/KS (881 amino acids) and JsCPS/KS (886 amino acids) sequences share 60% identity. To determine the regions and amino acids involved in 16α-hydroxy-ent-kaurane formation, we analyzed the enzymic functions of JsCPS/KS and PpCPS/KS chimeric proteins. When the C-terminal region of PpCPS/KS was exchanged with the JsCPS/KS C-terminal region, the chimeric cyclases produced only ent-kaurene. The replacement of PpCPS/KS Ala710 with Met or Phe produced a JsCPS/KS-type cyclase that converted GGDP to ent-kaurene as the sole product. In contrast, replacing Ala710 with Gly, Cys or Ser did not affect the PpCPS/KS product profile as much as replacement of Cys of JsCPS/KS by Ala. Thus, the hydrophobicity and size of the side chain residue at the PpCPS/KS amino acid 710 is responsible for quenching the ent-kauranyl cation by the addition of a water molecule.

The mono p-bromobenzoate of the diol derived from α-pompene has been studied by X-ray crystal structure analysis and determined to be 9-p-bromobenzoxy-8-hydroxy-1,2,6,8-tetramethyltricyclo[5.3.1.02,6]undecane. The crystals are of the orthorhombic space group P212121, a=46.53(2), b=12.20(2), c=7.39(2) A, Z=8, and hence there are two independent molecules per asymmetric unit. The structure was solved by the heavy-atom methods, and refined by block-diagonal least-squares calculations to a final R value of 0.103 for 2493 observed reflections. The structures of the two independent molecules in the asymmetric unit are quite similar. Both molecules contain a tricyclo[5.3.1.02,6]undecane ring in which three fused rings (cyclohexane, cyclopentane, and cyclopentane) are present. The overall configuration of these three fused rings can be described as a “cis” type. The conformation of the cyclohexane ring is of a chair form, and the two cyclopentane rings exhibit envelope forms. Based on the anomalous X-ray dispersi...

The title compounds, key intermediates in the syntheses of (±)-vitamin D3 and (±)-erythro-juvabione, have been prepared in short steps using stereoselective cleavage reactions of the cyclopropane derivatives.

During the course of investigation on constituents of liver-worts, four sesquiterpenoids showing opposite rotation, (−)-longiborneol, (−)-α-longipinene, (−)-longifolene and (+)-α-himachalene, were isolated from a Japanese liverwort. By preparation of derivatives and application of physical methods the absolute configuration of (−)-longiborneol, the main component, was elucidated as an optical antipode (I) of (+)-longiborneol isolated from higher plants.