The application of microwaves in organic chemistry has experienced exponential growth within the last eight years. Rate enhancements varied from 10 to 1500 times compared with those of conventionally heated samples. We propose here a new technology for preparation of diphenylamine by microwave-activation, using an inorganic solid support, namely bentonite. This method offers the following advantages over conventional synthesis of this compound: high efficiency, safety, the experimental procedure is much simpler and environmental friendly.

Synthesis and theoretical study of five new 2-oxopyranochromone-3-carbaldehydes, and their reactions with 2,4-dinitrophenylhydrazine and 2-benzothiazolylhydrazine were investigated.

We synthesized and characterized photolabile cholinergic ligands, and assessed their potential use in the exploration of the catalytical mechanism of acetylcholinesterase

In the course of our investigations concerning the regio- and stereochemical course of the inhibition of chymotrypsin and acetylcholinesterase (F.A. Merckling, P. Rüedi, Chimia 1994, 48, 279) we have prepared the chiral 2,4-dioxa-3l5-phosphabicyclo[4.4.0]decan-3-ones (1-8). Being configurationally and conformationally locked, these cis- and trans-decaline-type congeners are good probes for the investigation of stereochemical implications by 31P-NMR spectroscopy (W. Ganci, E.J.M. Meier, G. Przibille, U. Ringeisen, P. Rüedi, Chimia 1996, 50, 345; iid. Helv. Chim. Acta, 1997, 80, 421).

In continuation of our investigations concerning the regio- and stereo-chemical course of the inhibition of serine hydrolases (chymotrypsin, acetylcholinesterase) (F.A. Merckling, P. Rüedi, Chimia 1994, 48, 279) we have prepared conformationally restricted organophosphates of the cis- and trans-az(oni)adecaline type. Related compounds proved to be good probes for the investigation of stereochemical implications by 31P-NMR spectroscopy (W. Ganci, E.J.M. Meier, F.A. Merckling, G. Przibille, U. Ringeisen, P. Rüedi, Chimia 1996, 50, 345; iid. Helv. Chim. Acta, 1997, 80, 421).

Several structural factors are known to restrict the conformational flexibility of peptides, e. g. thioamide groups, a- or N-substitution, etc. For many years we have been interested in the constraints introduced by the presence of a-methylated a-amino acids, and with the 'azirine/oxazolone method' we have developed a convenient synthetic access to such peptides. 3-Amino-2H-azirines proved to be useful synthons for the introduction of a-substituted a-amino acids [1]. Conversion of 3-amino-2H-azirines with thiobenzoic acid, which leads to the corresponding thioamides, has shown the possibility of using a-amino thioacids in the 'azirine/oxazolone method' to sythesize endothiopeptides [2,3].

The taxol® family of molecules, exemplified by taxol®,1 and baccatin III has commanded the attention of some of the most eminent synthetic organic research teams in the world.2 This intense interest has been engendered by the unusual tetracyclic structure of this class of compounds, and more importantly, by the use of taxol® in cancer chemotherapy. This outstanding combination of attractive features has stimulated a huge variety of synthetic approaches directed towards the synthesis of taxol® itself, and simpler analogues which may also have desirable anti-cancer properties.

Optically active sulfinimines proved to be versatile chiral auxiliares in the synthesis of amino-compounds. In this presentation new camphor derived sulfinimine is described, as well as its reactions with some nucleophiles. Lewis acid catalyzed additions of ketene silyl acetal to sulfinimine is presented and hetero Diels-Alder reaction with Brassard's diene. As opposed to majority of sulfur containing chiral auxiliares, title compound may be recycled without loss of optical purity.

Antioxidant activitv guided fractionation of extracts of Plectranthus sylvestris (labiatae) yielded the novel alkyloxycatechols 1-3 (M. Juch, P. Rüedi, Helv. Chim. Acta 1997, 80, 436). The optically active natural products and several diastereomers have been synthesized. The open chain compounds are prepared by enantioselsective reduction of the corresponding aldol adduct and chromatographic separation of the diastereomers, the cyclic ones by biomimetic phenol oxidation of 2b.

(Final version not submitted in time.)