Decatrienes diastereoselection

The use of Lewis acid catalysis is a powerful method of increasing the rates and diastereoselectivity of many IMDA reactions. Several examples involving terminally activated nona- and deca-trienes are summarized in Tables 1 and 2. Examples illustrating rate and stereoselectivity improvements in the cycliza-timis of funcdmialized decatrien-3-ones appear in Figure The most striking of these is the... 

P. Herczegh, M. Zseby, L. Sziligyi, Z. Dinya, and R. Bogn r, High diastereoselection in the intramolecular Diels-Alder reaction of sugar-based l,7(E, 9-decatrienes, Tetrahedron 45 5995 (1989). 

Figure 28 Diastereoselectivity in IMDA reactions of conformationally mobile, monosubstituted 1,7,9-decatrienes and 1,6,8-nonatrienes sterically favored transition states...

To assess the diastereoselectivity and the intrinsic reactivity of prosolanapyrones, Diels-Alder reactions were examined under various conditions." In less polar solvents, heating was required for the effective cycloaddition of 136—138. Increase in the oxidation levels of the three substituents in the prosolanapyrones enhances rate acceleration. This can be rationalized in terms of the LUMO energy of the dienophile moiety in the pyrone precursors. Wo-/cxo-selectivities with 136—138 were essentially the same in various organic solvents, while the wt /o-selectivity was increased with increasing solvent polarity. The slight preference for f zfo-selectivity in less polar solvents suggests that there is little steric congestion in both endo- and cxo-transition states as reported in the reactions of simple decatriene systems." ... 

Chiral thiopyran derivatives have been obtained in Diels-Alder reactions from monosaccharide O-thioformates and dithiooxalates. Intramolecular Diels-Alder cyclization of 1,6,8-nonatrienes and 1,7,9-decatrienes prepared from pentoses or D-glucose afforded multichiral hexahydroindene and octahydronaphthalene derivatives with very high diastereoselectivity. 

Intramolecular Diels-Alder (IMDA) reactions of 1,6,8-nonatrienes and 1,7,9-decatrienes have been used frequently for the construction of chiral ring systems of complex natural products (18-20), Although saccharide derivatives have been employed many times in intermolecular Diels-Alder reactions (21-28) their IMDA reaction appears not to have been studied so far. The diastereoselectivity of IMDA reactions can be influenced, among other factors, by the size of substituents, and by the chirality of carbons of the connecting chain. Our aim was to study the possibilities of the application of single monosaccharides as tether chains in IMDA reactions. The influence of the presence of three or four chiral... 

Wang et aZ [1] have synthesized acyclic dienyne-allene alcohols, a precursor required for the construction of tetracyclic steroidal skeleton. The conjugated allenic aldehyde, 2,3,9-decatrienal, prepared [2] from readily available 1,2,8-nonatriene, undergoes condensation with allenylborane [3] smoothly and affords after treatment with 2-aminoethanol, hydroxyallendienyne in excellent isolated yield (Chart 6.20) [1]. Similar result is obtained with allenylborane (R = CH3). The diastereoselectivity of the two new formed stereocenters is high [de = 94%). 

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