Radhika Sanduja

The structure of PB-1, an unusual toxin isolated from the red tide dinoflagellate nttychodiscus brevis

The structure of PB-1, 1, an ichthyotoxin isolated from Ptychodiscus brevis was determined to be O,O-dĩnthenyl-N-cyclooctyl nthosnthoramidate.

STEROL DISTRIBUTION IN THE GENUS HETEROCAPSA (PYRRHOPHYTA)1

The sterol composition of seven strains of marine peridinioid dinoflagellates comprising the four known species of Heterocapsa Stein was examined by gas chromatography‐mass spectrometry to determine the utility of these compounds in systematics. Cholest‐5‐en‐3β‐ol (cholesterol), 24‐methyl‐cholest‐5‐en‐3β‐ol (24‐methylcholesterol), 4α,24(S)‐dimethyl‐5α‐cholestan‐3β‐ol (4,24‐dimethylcholestanol), 4α,23,24(R)‐trimethyl‐5α‐cholest‐22‐en‐3β‐ol (dinosterol), 4α,23ξ,24ξ‐trimethyl‐5α‐cholestan‐3β‐ol (dihydrodinosterol), and an unknown sterol were detected. Sterol composition does not vary significantly from species to species within the genus Heterocapsa and thus cannot be used for species differentiation. Sterols may, however, have value in defining the properties of dinoflagellate taxa above the family level. Over the course of the growth curve for Heterocapsa niei (Loeblich) Morrill & Loeblich 4,24‐dimethylcholestanol and dinosterol covaried, suggesting that 4,24‐dimethylcholestanol is converted into dinosterol by a previously proposed bioalkylation scheme.

Isolation and structure of a cytotoxic epoxy sterol from the marine mollusc Planaxis sulcatus

A novel epoxy sterol isolated from the marine mollusc Planaxis sulcatus has been identified as 9 alpha,11 alpha-epoxycholest-7-ene-3 beta,5 alpha,6 beta-triol by spectrometric methods.

Applications of cosy and homonuclear relay 2D-NMR in the determination of the structure of new cembrane isolated from the mollusc planaxis sulcatus

Abstract Proton-proton homonuclear chemical shift correlation (COSY) and homonuclear relayed coherence transfer (RELAY) have been used to establish the structure of 3,11-diacetoxy-15,16-dehydrocembran-6-one.

Isolation and crystal structure of 5-hydroxy-2,8-dimethyl-6,7-dimethoxybenzopyran-4-one from Couepia paraensis

Abstract A highly substituted chromone constituent of Couepia paraensis was isolated and identified as 5-hydroxy-2,8-dimethyl-6,7-dimethoxychromone by spect

Structure of 3-O-acetylgibberellin A3

C21H24O7, Mr = 388.4, orthorhombic, P2(1)2(1)2(1), a = 13.279 (10), b = 15.615 (10), c = 9.427 (8) A, V = 1954.7 A3, Z = 4, D chi = 1.319 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 1.0 cm-1, F(000) = 824, T = 293 K, R = 0.049 for 1805 observed reflections. The gibberellane skeleton shows the conformational variety characteristic of many other gibberellin derivatives. Ring A is in a sofa conformation while the five-membered ring B assumes an intermediate conformation between an envelope and a half-chair. The lactone ring is in an ideal envelope conformation and shows a marked difference in its two C-O distances. Each molecule is hydrogen bonded to two others to form continuous spiral chains along the c axis.

Echinolactone A and B: isolation and structures of two novel lactones from the marine coelenterate Echinopora lamellosa

Two novel pentacyclic triterpenes were isolated from the marine coelenterate Echinopora lamellose; their structures and absolute configuration (determined from spectroscopic and X-ray diffraction data) are reported.