Structure Determination of a Natural Juvenile Hormone Isolated from a Heteropteran Insect

Juvenile hormone (JH), which occurs in several forms in different insects, is one of the most important insect hormones. The structure of JH in Heteroptera has not been elucidated until recently, although insects in this suborder have long been used as experimental animals for JH research. Here we review the structure determination of a novel JH in a stink bug, Plautia stali, which was named juvenile hormone III skipped bisepoxide [JHSB3: methyl (2R,3S,10R)-2,3;10,11-bisepoxyfarnesoate], based on the arrangement of two epoxides at C2,3 and C10,11 with a skipped double bond at C6,7

Short Total Synthesis of (−)-Kainic Acid

A short total synthesis of (−)-kainic acid has been developed involving a novel diastereofacial differentiating Cu-catalyzed Michael addition–cyclization reaction, which provided access to a chiral pyrroline in a highly stereoselective manner. The chiral pyrroline was converted to (−)-kainic acid via the stereoselective 1,4-reduction of the pyrroline double bond in three steps

Stereocontrolled Synthesis of 19′-Deoxyperidinin

The stereocontrolled convergent synthesis of 19′-deoxyperidinin, <b>2</b>, which might be a useful peridinin analog to understand the ICT characteristics, was efficiently achieved by sequential Pd-catalyzed cross-coupling reactions using bidirectionally extensible conjugated C5 olefin segments. The crucial 5­(2<i>H</i>)-ylidene­dihydro­furan function of <b>2</b> was successfully constructed by the Au-catalyzed regio- and stereoselective 5-exo-dig etherification

Characterization of Class IB Terpene Synthase: The First Crystal Structure Bound with a Substrate Surrogate

Terpene synthases (TS) are classified into two broad types, Class I and II, based on the chemical strategy for initial carbocation formation and motif sequences of the catalytic site. We have recently identified a new class of enzymes, Class IB, showing the acceptability of long (C₂₀–C₃₅) prenyl-diphosphates as substrates and no amino acid sequence homology with known TS. Conversion of long prenyl-diphosphates such as heptaprenyl-diphosphate (C₃₅) is unusual and has never been reported for Class I and II enzymes. Therefore, the characterization of Class IB enzymes is crucial to understand the reaction mechanism of the extensive terpene synthesis. Here, we report the crystal structure bound with a substrate surrogate and biochemical analysis of a Class IB TS, using the enzyme from Bacillus alcalophilus (BalTS). The structure analysis revealed that the diphosphate part of the substrate is located around the two characteristic Asp-rich motifs, and the hydrophobic tail is accommodated in a unique hydrophobic long tunnel, where the C₃₅ prenyl-diphosphate, the longest substrate of BalTS, can be accepted. Biochemical analyses of BalTS showed that the enzymatic property, such as Mg^2⁺ dependency, is similar to those of Class I enzymes. In addition, a new cyclic terpene was identified from BalTS reaction products. Mutational analysis revealed that five of the six Asp residues in the Asp-rich motifs and two His residues are essential for the formation of the cyclic skeleton. These results provided a clue to consider the application of the unusual large terpene synthesis by Class IB enzymes