Ti(III)-Promoted Radical Cyclization of Epoxy Enones. Total Synthesis of (+)-Paeonisuffrone
摘要:
The total synthesis of (+)-paeonisuffrone starting from (+)-10-hydroxycarvone is described. The key step of our synthetic strategy is a titanium-catalyzed stereoselective cyclization initiated by epoxide opening through electron transfer. This reaction stereoselectively affords the highly oxygenated pinane skeleton present in the target molecule and opens a new and effective approach to the synthesis of the complex, biologically active terpenoids isolated from the roots of the Chinese paeony (Paeonia albiflora Pallas and Paeonia suffruticosa Andrews).
Ansellane型酯类萜类化合物包括ansellones A-G和(+)-phorbadione是结构新颖的海洋次级代谢产物,具有抗癌和抗HIV活性。从(+)-香紫苏内酯起16至23步完成了三个结构上具有代表性的成员(-)-杏仁糖A和B和(+)-佛巴丹酮的第一个不对称全合成。这条路线的特点是通过内部醇亲核试剂以1,4加成方式(S N 2')对乙烯基环氧化合物进行第一次区域选择性环化。此外,烯丙基CH氧化是在合成(-)-鞣酸A和(+)-佛手瓜酮的后期进行的。预期该策略可适用于其他茴香油酯类萜类化合物的合成。
Ti(III)-promoted cyclizations. Application to the synthesis of (E)-endo-bergamoten-12-oic acids. Moth oviposition stimulants isolated from Lycopersicon hirsutum
as the key step to access the diol 10 as a convenient starting material of the target molecules. The synthesis of β-(E)-endo-bergamoten-12-oic acid 2a from (+)-8,9-epoxycarvone 8 was successfully achieved by Suzuki–Miyaura coupling of the terminal alkene 20 with β-iodomethacrylate 21c, followed by deprotection and dehydration processes. Moreover, synthesis of the α-(E)-endo-1-hydroxy-bergamoten-12-oic
Functionalized α,α-Dibromo Esters through Claisen Rearrangements of Dibromoketene Acetals
作者:Nathan J. Dupper、Ohyun Kwon
DOI:10.1021/acs.orglett.5b00209
日期:2015.2.20
Allylic alcohols can be transformed into gamma,delta-unsaturated alpha,alpha-dibromo esters through a two-step process: formation of a bromal-derived mixed acetal, followed by tandem dehydrobromination/Claisen rearrangement. The scope and selectivity of both steps have been investigated. The product alpha,alpha-dibromo esters were subjected to various carbon-carbon bond-forming reactions, oxidations, and lactonizations.