Stereocontrolled Syntheses of the Nemorensic Acids Using 6-Diazoheptane-2,5-dione in Carbonyl Ylide Cycloadditions
作者:David M. Hodgson、Frédéric Le Strat、Thomas D. Avery、Andrew C. Donohue、Tobias Brückl
DOI:10.1021/jo048446b
日期:2004.12.1
6-diazoheptane-2,5-dione (9) serves as a common precursor in a formal synthesis of frontalin 19, and in syntheses of cis-nemorensic acid 1, 4-hydroxy-cis-nemorensic acid 2, 3-hydroxy-cis-nemorensic acid 3, and nemorensic acid 4. The key step in these syntheses is the Rh2(OAc)4-catalyzed tandem carbonyl ylide formation−intermolecular 1,3-dipolar cycloadditions of diazodione 9 with formaldehyde, alkynes or allene, which
乙酰丙酸衍生的6- diazoheptane -2,5-二酮(9)用作在frontalin正式合成的共同前体19,而在合成顺-nemorensic酸1,4-羟基-顺式-nemorensic酸2,3 -羟基-顺-nemorensic酸3和nemorensic酸4。这些合成的关键步骤是Rh 2(OAc)4催化的串联羰基内酯的形成-重氮二酮9的分子间1,3-偶极环加成反应与甲醛,炔烃或丙二烯发生,具有很高的区域选择性。最初衍生自环状羰基叶立德中间体的环的随后的氧化裂解提供了直接进入多取代的四氢呋喃的途径,并且特别是有效地进入了肾上腺素酸。使用手性铑催化剂与重氮二酮9进行对映选择性环加成反应,可得到高达51%ee的环加合物。