R. Kazlauskas

New diterpene isocyanides from a sponge

Abstract Six new diterpene isocyanides have been isolated from a sponge ( Adocia sp.). Their structures support the biosynthetic suggestion for the formation of diisocyanoadociane reported from the same sponge.

Five new C26tetracyclic terpenes from a sponge (Lendenfeldiasp.)

Five new scalarane sesterterpenes have been isolated from a Western Australian sponge (Lendenfeldia sp.). As with earlier reported examples of these compounds, several of these metabolites of this sponge are extremely potent inhibitors of platelet aggregation.

Profiling of urinary testosterone and luteinizing hormone in exercise-stressed male athletes, using gas chromatography-mass spectrometry and enzyme immunoassay techniques

Knowledge of the effects of episodic or short-term exercise-stress on endogenous testosterone and luteinizing hormone levels still remains fragmentary and inconclusive. In this study, an approach based on the absolute concentrations of urinary total testosterone (T), luteinizing hormone (LH) and the T/LH concentration ratios, was used to profile short-term exercise-stress responses in healthy drug-free male athletes. Testosterone and luteinizing hormone concentrations were measured using gas chromatography-mass spectrometry (GC-MS) and microparticle enzyme immunoassay (MEIA) techniques, respectively. Stress profiles derived from exercise-stress at VO2max, 68.1% VO2max and 51.6% VO2max were plotted using the concentrations of T, LH and the ratios of T/LH found under non-stressed and stressed conditions. Significant changes in LH concentrations (p < 0.005) and T/LH ratios (p < 0.005) levels were observed between the pre-stress and post-exercise conditions during acute exercise-stress at VO2max but the T concentration did not show any marked change relative to the non-stressed condition. Whilst exercise-stress appeared to reduce the change in T concentrations between the pre- and post-exercise states compared to that in the non-stressed control condition, the change in LH concentrations showed a moderate increase at submaximal oxygen uptake values. The stress profiles derived from this study facilitated an assessment of the relationship between the endogenous T, LH and T/LH ratio stress-responses over a short period of applied exercise-stress.

Two derivatives of farnesylacetone from the brown algaCystophora moniliformis

Farnesylacetone epoxide (3) and the isomeric diketone (4) have been isolated from the brown algaCystophora moniliformis.

Synthesis of analogues of γ-aminobutyric acid. Part 11. Unsaturated and saturated tetronic acid [furan-2,4(3H,5H)-dione] derivatives

5-(2-Aminoethylidene)-4-hydroxyfuran-2(5H)-one (3) and the corresponding reduced 5-(2-aminoethyl) derivative (4) have been synthesised as conformationally restricted analogues of the neurotransmitter GABA. The use of the t-butyl protected reagents bis(t-butoxycarbonyl) amine and 5-ethylidene-4-t-butoxyfuran-2(5H)-one (7b) allowed generation of the required amino compounds under mild acidic deprotection conditions in the final step.

Two cembranes fromCespitulariaspecies (soft coral)

Two new cembranolides, (1R,2S,3E,7R,8R,11E,14S)-7,8-epoxy-14-hydroxycembra-3,11,15-trien-17,2-olide and (lR,2R,3E,7R,SR,11E,14R)-7,8-epoxy-14-hydroxycembra-3,11,15-trien-17,2-olide, have been isolated from separate species of Cespitularia (soft coral).

Carotenoids from the marine sponge lanthella basta

The carotenoid composition of the marine sponge lanthella basta is reported. Identifications were based on electronic-, mass-, 1H NMR-, IR- and CD spectra in comparison with authentic carotenoids. Group A (phytoplankton-type carotenoids) comprised β,ϵ-carotene, β,β-carotene, mutatochrome, β-cryptoxanthin, mutatoxanthin and fucoxanthin. Group B (sponge metabolized carotenoids), 65% of total carotenoid, consisted of bastaxanthin B, C, D, E and F. The bastaxanthins are novel carotenoid sulphates.

Furodendin, a C22 degraded terpene from the spongePhyllospongia dendyi

The structure of furodendin (5), a minor secondary metabolite of the spongePhyllospongia dendyi, has been solved by spectral methods. Furodendin is probably derived, biosynthetically, by elimination of a C3 unit from a C25 geranyl-farnesol precursor.

Biosynthesis. Part 24. Speculative incorporation experiments with 1-benzylisoquinolines and a logical approach via C6–C2 and C6–C3 precursors to the biosynthesis of hasubanonine and protostephanine

Many possible 1-benzyltetrahydroisoquinolines have been examined as possible advanced precursors of the alkaloids hasubanonine (1) and protostephanine (2) in Stephania japonica plants, but none was incorporated significantly. Administration of various precursor molecules having only one aromatic ring, such as tyrosine, has demonstrated that both alkaloids are derived from two different C6–C2 biogenetic units. The subsequent failure of further 1-benzyltetrahydroisoquinolines and bisphenethylamines to be incorporated suggested the intermediacy of either (a) modified 1-benzylisoquinolines or (b) trioxygenated C6–C2 building blocks. Precursors designed to examine the first possibility, such as 1-benzyl-3,4-dihydroisoquinolines or 1-benzyl-1-carboxytetrahydroisoquinolines, were not incorporated into (1) and (2) whereas two 3′,4′,5′-trioxygenated 2-phenylethylamines were incorporated. These findings allow further delineation of the requirements for later precursors of the alkaloids (1) and (2).

Biosynthesis. Part 23. Degradative studies on the alkaloids hasubanonine and protostephanine from Stephania japonica

Degradative schemes are reported for the alkaloids hasubanonine (1) and protostephanine (2) of Stephania japonica to allow labelling patterns to be determined. Acetolysis of (1) leads eventually to a phenanthrene (5c) by removal of the ethanamine bridge. N-Methylation and Hofmann elimination of (2) gives one major olefinic product, assigned structure (6a) from 1H n.m.r. data and confirmed by synthesis of specifically 13C-labelled material.