I. Preparation of some Dipterex Analogues and stability of O,O-Dimethyl-2,2,2-Trichloro-1- Methoxyethyl Phosphonate

Dipterex and its homologues have been prepared by a single vessel reaction in good yields. The stability of O,O-dimethyl-2,2,2-trichloro-1-methoxyethyl phosphonate Ib towards temperature and pH variation has been studied using P32-labelled compounds. Compared with the parent substance (Dipterex), Ib is much more stable.

The anticholinesterase activity of Dipterex was found to be over 300 times higher than that of the methyl ether Ib; thus proving that the presence of the free hydroxyl group in Dipterex and its anticholinesterase activity are correlated.

Chemical diversity in opisthobranch molluscs from scarcely investigated Indo-Pacific areas

Opisthobranch molluscs with both a rich variety of secondary metabolites and great biomedical potential represent the most intensively studied group of molluscs in natural product chemistry. We review here the chemical investigations into secondary metabolites of "sea slugs" from less-studied Indian, Chinese and Egyptian coasts, giving an overview of their most relevant biological activities. In addition to the biomedical interest of the metabolites, in which both structures and organisms often lose their own importance, this chapter emphasizes the phyletic and geographic distribution of the compounds in order to provide a further informational base for chemotaxonomical generalizations.

On the Properties of Some α-Hydroxy Phosphonates and Related Compounds

In search for effective organophosphorus esters against the larva of the cotton leaf worm (Prodenia litura F), some α-hydroxy phosphonic acid dimethyl esters and related compounds have been synthesized. The effect of substitution on the antiesterase activity and toxicity towards Prodenia larvae has been investigated.

The infra-red spectra of the prepared phosphorus esters are discussed.