A Study of the Photochemistry of Benzobicyclo[2.2.2]octan-2-ones

The anti- and syn-3-methyl isomers of 5,8-dimethoxy-1,3-dimethyl-3,4-dihydro-1,4-ethanonaphthalen-2(1H)-one (2) and (3) and the 1,3,3- trimethyl analogue (4) were prepared from the Diels -Alder adduct of benzoquinone and 1,3-dimethylcyclohexadiene. The photochemistry of each has been studied and the structures of several photoproducts have been assigned. One of the products from irradiation of (3) was found by X-ray analysis to be a 1,4-disubstituted 1,2,3,4- tetrahydronaphthalene [methyl 2-(5′,8′-dimethoxy-4z′-methyl-1′,2′,3′,4′-tetrahydronaphthalen-1′-yl) propanoate ] with the unexpected cis-stereochemistry (11). Irradiation of (4) produces, inter alia, a compound containing the unusual tetracyclo [7.4.0.02,7.04,8] trideca -1(9),10,12-triene skeleton whose structure was determined by n.m.r. spectroscopy.

Structural Studies of Aromadendrane-1,2-diols

The structures of two aromadendranediols derived from the naturally occurring sesquiterpenes (+)-ledene and (+)-spathulenol have been determined by X-ray crystallographic methods.

Structural Study of an Acyclic Diterpene From Eremophila Species

The solid-state structure of the semicarbazone derivative (3) of the aldehyde diacid (1), an acyclic diterpene isolated from Eremophila species, has been determined by a single-crystal room-temperature X-ray study. Crystals of (3) are triclinic, Pī , a 14.642(7), b 14.371(6), c 12.823(6) Ǻ, α 76.59(4), β 66.09(4), γ 72.97(4)°, Z = 4; R was 0.052 for 2265 independent 'observed' (I > 3σ(I)) diffractometer reflections.

Reinterpretation of the evidence for the structure of isoaurostatin

The spectroscopic parameters used to assign the structure to isoaurostatin (4',6-dihydroxyisoaurone), a metabolite isolated from Thermomonospora alba, have been reinterpreted. It is suggested that isoaurostatin is identical to the isoflavone daidzein.

Structural Study of an ent-Kaurane Lactone

The structure of the methyl ester derivative (2) of ent-20-hydroxy-16βH-kaurane-17,19-dioic acid 19,20-lactone has been determined by X-ray crystallographic methods. The δ-lactone ring adopts the chair conformation both in the solid state and in solution.

Trichoderma secondary metabolites that affect plant metabolism

Recently, there have been many exciting new developments relating to the use of Trichoderma spp. as agents for biocontrol of pathogens and as plant growth promoters. Several mechanisms have been proposed to explain the positive effects of these microorganisms on the plant host. One factor that contributes to their beneficial biological activities is related to the wide variety of metabolites that they produce. These metabolites have been found not only to directly inhibit the growth and pathogenic activities of the parasites, but also to increase disease resistance by triggering the system of defence in the plant host. In addition, these metabolites are also capable of enhancing plant growth, which enables the plant to counteract the disease with compensatory vegetative growth by the augmented production of root and shoot systems. This review takes into account the Trichoderma secondary metabolites that affect plant metabolism and that may play an important role in the complex interactions of this biocontrol agent with the plant and pathogens.

Isoprenylated flavanones and dihydrochalcones from Macaranga trichocarpa

Two isoprenylated flavanones, macatrichocarpins A and B, and two isoprenylated dihydrochalcones, macatrichocarpins C and D, have been isolated and identified from the acetone extract of the leaves of Macaranga trichocarpa. The structures of these compounds were determined based on spectroscopic data, including UV, IR, 1D and 2D NMR spectroscopic and HREIMS data. This is the first report of the presence of dihydrochalcone derivatives in the genus Macaranga.

Structural Study of ( - )-Isopimara-9(11),15-diene-3-β,19-diol

The structure of (-)-isopimara-9(11),15-diene-3β,19-diol (1) has been confirmed by single crystal X-ray crystallographic methods. The conformations in the solid state and in solution are similar.

Synthesis of deuterated ent-beyeranes. Stereospecific reduction of a 4-axial aldehyde

Reduction of the 4a-axial aldehyde group in ent-3,19-dioxobeyer-15-en-17-oic acid (1) by sodium borohydride is shown to occur by attack on the Si-face of the carbonyl group. The synthesis of some ent-beyerane derivatives stereospecifically labelled with deuterium at C19 is described.

Phenolic derivatives with an irregular sesquiterpenyl side chain from Macaranga pruinosa

A stilbene and two flavonoid derivatives, macapruinosins A-C (1-3), together with two known flavonoids, papyriflavonol A and nymphaeol C, have been isolated from the acetone extract of the leaves of Macaranga pruinosa. The structures of these compounds were identified based on spectral data analysis. Compounds 1 and 2 are the first examples of natural compounds containing an irregular sesquiterpenyl side chain with a cyclobutane skeleton.