Many biologically interesting eudesmanolides have been synthesized from commercilly available a-santonin and their biological activities have been studies. The eudesmanolides functionalized at C-1 were then demonstrated to be efficient common intermediates for the syntheses of elemanolides and guaianolides. Thus the fragmentation reaction of 36 with Al(iPrO)3 gave a new route to the synthesis of elemanolides and germacranolides. The solvolytic rearrangement of 36, 49, 63, and 99 gave efficient intermediates for the syntheses of naturally occurring guaianolides
Recently, a variety of S, N-heterocycles has been developed to the useful and practical drugs in agrochemicals and medicines. Under this circumstance, we paid our attention to these heterocycles as screening target compounds, to create new bioactive heterocycles. As a methodology to search for the new lead compounds, we focussed on the synthetic development of S, N-heterocycles. In result, this synthetic approach led to the generation of heterocycles with either the insecticidal or the anti-PAF activity. On the basis of their structureactivity relationships, these heterocycles were extended to the optimized compounds leading to novel bioactive heterocycles, triazolobenzothiazoles and thiazolidin-4-ones. In this article, the synthetic approach to S, N-heterocycles with biological activities is described.
Syntheses and chemical properties for 4 H-1, 3-oxazin-4-one (1) and 6 H-1, 3-oxazin-6-one (2), which have appeared in the literature since 1980, are reviewed, including methods for the preparation of 1 by [4π+2π] cycloaddition reaction and dehydration-cyclization of acylacetylcarboxamides, and of 2 by thermal cyclization via N-acyliminoketene. Ring transformations of 1 and 2, such as the ring-opening of 1 followed by recyclization, and cycloaddition reaction of 2 as an azadiene, are discussed therein.
To construct artificial flavoenzymes, it would be of primary importance to exploit oxidation-active flavin model compounds, which are quite usefull not only for exploitation of new oxidation but also for turnover redox catalyst under aerobic conditions. In this article, we describe new oxidations exploited by employing the oxidation-active flavin mimics and functionalized oxidation-active flavin mimics.
Carbonates of propargyl alcohol and its functionalized derivatives undergo various palladium-catalyzed reactions under mild neutral conditions. Their reacton with olefins affords 1, 2, 4-trienes, and 1, 2-dien-4-ynes are obtained by the reaction with terminal acetylenes. Reaction with soft carbonucleophiles is a good synthetic method for furans. Also 2-(1-alkynyl)oxiranes react with β-keto esters to form furans. Allenyl esters (2, 3-dienoates) and their derivatives such as α-alkylidene-β-lactams and alkylidenecyclopentenonecarboxylates are obtained by the carbonylation of various functionalized propargyl carbonates. Allenes (1, 2-dienes) are formed by the hydrogenolysis with formic acid.