A Formal Total Synthesis of (+)-Tetronolide, the Aglycon of the Tetrocarcins: Enantio- and Diastereoselective Syntheses of the Octahydronaphthalene (Bottom-Half) and Spirotetronate (Top-Half) Fragments
摘要:
A formal total synthesis of (+)-tetronolide, the aglycon of the tetrocarcins, has been achieved by virtue of the development of highly diastereo-and enantioselective syntheses of the bottom- and top-half fragments 4 and 5 reported herein. These fragments previously served as key intermediates in Yoshii's pioneering total synthesis of (+)-tetronolide, The synthesis of the bottom-half octahydronaphthalene unit 4 features the intramolecular Diels-Alder reaction of tetraenal 20 and proceeds in 17 steps and 5-6% yield from D-glyceraldehyde pentylidene acetal 8. The synthesis of the spirotetronate fragment 5 features the highly enantioselective exo selective Diels-Alder reaction of triene 37 and chiral dienophile 25b and proceeds in 14 steps and 10% overall yield from cis-2-butene-1,4-diol (38). An enantioselective synthesis of Boeckman's top-half cyclohexene fragment 6 sia the exo selective Diels-Alder reaction of diene 24 and dienophile 25a was also developed, but this route was deemed too inefficient for use in a projected total synthesis of the natural product. The syntheses of 5 and 6 provide important information on the utility of chiral dienophiles 25a and 25b in organic synthesis.
A Formal Total Synthesis of (+)-Tetronolide, the Aglycon of the Tetrocarcins: Enantio- and Diastereoselective Syntheses of the Octahydronaphthalene (Bottom-Half) and Spirotetronate (Top-Half) Fragments
作者:William R. Roush、Melissa L. Reilly、Kazuo Koyama、Bradley B. Brown
DOI:10.1021/jo970960c
日期:1997.12.1
A formal total synthesis of (+)-tetronolide, the aglycon of the tetrocarcins, has been achieved by virtue of the development of highly diastereo-and enantioselective syntheses of the bottom- and top-half fragments 4 and 5 reported herein. These fragments previously served as key intermediates in Yoshii's pioneering total synthesis of (+)-tetronolide, The synthesis of the bottom-half octahydronaphthalene unit 4 features the intramolecular Diels-Alder reaction of tetraenal 20 and proceeds in 17 steps and 5-6% yield from D-glyceraldehyde pentylidene acetal 8. The synthesis of the spirotetronate fragment 5 features the highly enantioselective exo selective Diels-Alder reaction of triene 37 and chiral dienophile 25b and proceeds in 14 steps and 10% overall yield from cis-2-butene-1,4-diol (38). An enantioselective synthesis of Boeckman's top-half cyclohexene fragment 6 sia the exo selective Diels-Alder reaction of diene 24 and dienophile 25a was also developed, but this route was deemed too inefficient for use in a projected total synthesis of the natural product. The syntheses of 5 and 6 provide important information on the utility of chiral dienophiles 25a and 25b in organic synthesis.
Total synthesis of tetronolide, the aglycon of tetrocarcins
The first total synthesis of tetronolide (1) has been achieved via coupling of spirotetronate 3 with octahydronaphthalene aldehyde 17 and subsequent macrocyclization of ω-sulfone-α-aldehyde 2, leading to confirmation of the absolute configuration of 1.