Nonatrienes diastereoselection

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

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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