Enantioselective Total Synthesis of <i>Nitraria</i> Alkaloids: (+)-Nitramine, (+)-Isonitramine, (−)-Isonitramine, and (−)-Sibirine via Asymmetric Phase-Transfer Catalytic α-Allylations of α-Carboxylactams
作者:Jewon Yang、Yohan Park、Sehun Yang、Geumwoo Lee、Min Woo Ha、Mi-hyun Kim、Suckchang Hong、Hyeung-geun Park
DOI:10.1021/acs.joc.0c02573
日期:2021.3.19
bromide to (R,R)-NAS bromide afforded (−)-isonitramine (98% ee, 41% yield). (−)-Sibirine was synthesized by N-ethoxycarbonylation of (−)-isonitramine followed by reduction (98% ee, 14 steps, 32% yield). Furthermore, the diastereoselective reduction of (R)-2-benzhydryl-2-azaspiro[5.5]undecane-1,7-dione [(R)-15] followed by reductive removal of the diphenylmethyl group successfully gave (+)-nitramine (98%
在生物活性的天然产物中经常发现许多旋光的2-氮杂螺环结构。尤其是,Nitraria生物碱,(+)-硝胺,(+)-异烟酰胺,(-)-异烟酰胺和(-)-西比林碱在其2-azaspiro [5,5]十一烷-7的季碳上具有立体异构性。 -ol结构。为了合成Nitraria生物碱,我们通过α-叔丁氧羰基内酰胺的α-烷基化开发了一种新的对映选择性合成方法,用于手性α-季内酰胺。α-α-烷基化叔-butoxycarboxylactams在相转移催化(PTC)系统的情况(固体KOH,甲苯,-40℃)凭借(催化作用的小号,小号)-NAS溴化物(5 mol%)以非常高的化学性质(<99%)和对映选择性(<98%ee)提供了相应的α-烷基-α-叔丁氧羰基内酰胺。我们的催化方法已成功地用于白背生物碱的对映选择性全合成。通过对映选择性相转移催化烯丙基化,Dieckmann缩合和非对映选择性还原作为关键反应,从δ-戊