John C. Roberts

Marine sterols. V. sterols of some tunicata. The occurrence of saturated ring sterols in these filter-feeding organisms

Abstract The sterols present in one oceanic and two coastal tunicates have been determined by combined gas chromatography-mass spectrometry techniques. Very complex sterol profiles were found in a Pyrosoma sp. and Ascidia mentula O. F. Muller, with 25 and 27 sterols, respectively, in which a high proportion of the sterols were identified as saturated ring compounds. The analyses established the presence of related pairs of 5α-stanols and Δ5-sterols with identical sidechains, whereas Δ7-sterols were almost absent in these extracts. A number of the 5α-stanols found are very uncommon in the marine environment and the presence of new C31 and C32 sterols with long sidechains indicated in the Ascidia mentula extracts is notable. Extracts of the coastal species, Ciona intestinalis L., were much simpler and contained only 13 sterols, some of which were saturated ring compounds.

NEOPENTYL ESTER PROTECTING GROUPS FOR ARYLSULFONIC ACIDS

Abstract We report that neopentylsulfonate esters are stable to a variety of standard organic reaction conditions and are easily cleaved to sulfonic acids. We also discuss the use of N-Boc-4-amino-2,2-dimethylbutyl-1-sulfonate esters which may be cleaved under conditions that are suitable for solid phase synthesis.

The structure of mangiferin

Abstract Further evidence is presented in confirmation of the structure 2- C -β- d -glucopyranosyl-1,3,6,7-tetrahydroxy-xanthone ( I ) for mangiferin.

Marine sterols—VII. The sterol compositions of oceanic and coastal marine annelida species

Abstract 1. 1. The sterol compositions of two oceanic and three inter-tidal zone species of annelid have been analysed by combined GC-MS techniques and the results compared with previous analyses. 2. 2. It was found that the oceanic annelids had more complex sterol profiles in which small quantities of 5α-stanols were present, whereas in the simpler profiles of the intertidal zone species, 5α-stanols were normally absent. 3. 5. It was also found that lugworm species from South Africa and South Wales contained substantially identical sterol compositions.

A synthesis of mangiferin

Abstract A synthesis of mangiferin (I), 2- C -β- D -glucopyranosyl-1,3,6,7-tetrahydroxy-xanthone, is described.

Marine sterols. XII. The sterols of some pelagic marine crustaceans

Abstract The sterol composition of some pelagic crustaceans (three species of pelagic euphausiids, one species of a bathypelagic marine mysid and one species of an estuarine mysid, two species of pelagic marine copepods, and one species of a bathypelagic marine copepod) have been determined by gas chromatographic-mass spectrometric techniques. The euphausiids appear to have developed an almost unispecific requirement for cholesterol, irrespective of trophic level, whilst the mysids show a considerable variation in sterol composition. The two near-surface copepod species contain a significantly greater variety of sterols than their bathypelagic counterpart. The results are compared with the known sterol compositions of other crustaceans in the marine food web and with phytoplankton. The extent of modification of dietary sterols after ingestion is discussed.

The sterols of some marine teleosts

Abstract 1. 1. The results of detailed sterol analysis on four mesopelagic myctophids, one mesopelagic species of stomiatoid and one pseudoceanic species of Macrorhamphosidae are presented. 2. 2. Attempts are made to compare the sterol composition of the fish to their likely dietary input of sterols. 3. 3. Although cholesterol is the major sterol in all samples up to ten other components sterols have been identified ( of the total sterols), some clearly being important structural sterols. 4. 4. Several of these sterols are known to occur in phytoplankton, tunicates, annelids and holothurians but this is believed to be the first report of significant levels of such sterols in marine vertebrates.

Aflatoxins and Sterigmatocystins

In this review the term mycotoxicosis refers to poisoning of man or animals by ingestion of foodstuffs contaminated with certain moulds and/or with their metabolic products (mycotoxins).

Quasiphosphonium intermediates. Part 3. Preparation, structure, and reactivity of alkoxyphosphonium halides in the reactions of neopentyl diphenylphosphinite, dineopentyl phenylphosphonite, and trineopentyl phosphite with halogenomethanes and the effect of phenoxy-substituents on the mechanism of alkyl–oxygen fission in Michaelis–Arbuzov reactions

The reactions of neopentyl diphenylphosphinite with chloro-, bromo-, or iodo-methane and of dineopentyl phenylphosphonite with bromo- or iodo-methane yield crystalline alkoxyphosphonium halides. In deuteriochloroform these intermediates decompose by a first-order process which involves rate-determining collapse of the phosphonium halide ion-pair with SN2-type fission of the alkyl–oxygen bond. Rates for chloride, bromide, and iodide are similar. In a more ionising medium (deuterioacetonitrile) dissociation leads to stabilisation of the intermediates and to deviation from first-order decomposition. Previously determined X-ray diffraction data for the bromides, together with relative rates of decomposition in deuteriochloroform for intermediates in the series Phn(RO)3–n[graphic omitted]MeX–(n= 0, 1, or 2) suggest that the stability and reactivity of alkoxyphosphonium intermediates are determined largely by inductive rather than mesomeric effects of ligands. The presence of phenoxy-substituents on phosphorus may cause a tendency towards SN1-type fission of the alkyl–oxygen bond in certain circumstances.

Sterols of the Cephalopod Spirula Spirula

The sterol biochemistry of the highly advanced molluscan class – the cephalopods – is poorly understood. Few analyses of their component sterols have been published in which GC-MS has been employed (Voogt, 1973; Idler et al. 1978; ApSimon & Burnell, 1980) and these have only involved 5 species. From the available data the cephalopods appear to have a much simpler sterol make-up than the other less-advanced molluscs. Cholesterol appears to be easily the predominant sterol ( ca . 90%) with minor amounts of up to 10 other common marine sterols. Of the species analysed, four ( Sepia officinalis, Octopus vulgaris, Eledone aldrovandi and Illex illecebrosus) had a very similar major and minor sterol composition. Only the more primitive Nautilus sp. (Idler et al. 1978) had a noticeably different minor sterol composition. Voogt (1973) reported cephalopods to be able to synthesise sterols though molluscs generally appear only to be able to carry out this biosynthesis slowly (Goad, 1978). Cephalopods are extremely active carnivores and thus would be expected to have a diverse diet. If their component sterols are of a dietary origin, a considerable variation in their minor sterol composition might be expected on the basis of the range in sterol composition reported for pelagic organisms (e.g. Morris & Culkin, 1977), many of which may be possible dietary components. Detailed knowledge however of cephalopod diets is limited. Quite apart from the fact that healthy specimens are rarely caught in nets, those that are caught often feed voraciously on the other organisms trapped in the net prior to being brought on board for examination.