523-06-8Relevant academic research and scientific papers
Catalytic Intramolecular Conjugate Additions of Aldehyde-Derived Enamines to α,β-Unsaturated Esters
Girvin, Zebediah C.,Lampkin, Philip P.,Liu, Xinyu,Gellman, Samuel H.
, p. 4568 - 4573 (2020/06/05)
We report a pairing of known catalysts that enables intramolecular conjugate additions of aldehyde-derived enamines to α,β-unsaturated esters. Despite extensive prior exploration of conjugate additions of aldehyde-derived enamines, catalytic conjugate additions to unactivated enoate esters are unprecedented. Achieving enantioselective and diastereoselective six-membered ring formation requires the coordinated action of a chiral pyrrolidine, for nucleophilic activation of the aldehyde via enamine formation, and a hydrogen bond donor, for electrophilic activation of the enoate ester. Proper selection of the hydrogen bond donor is essential for chemoselectivity, which requires minimizing competition from homoaldol reaction. Utility is demonstrated in a six-step synthesis of (-)-yohimbane from cycloheptene.
A Chiral Pentenolide-Based Unified Strategy toward Dihydrocorynantheal, Dihydrocorynantheol, Protoemetine, Protoemetinol, and Yohimbane
Xie, Changmin,Luo, Jisheng,Zhang, Yan,Zhu, Lili,Hong, Ran
supporting information, p. 3592 - 3595 (2017/07/15)
An organocatalytic cross-aldol reaction of formaldehyde (formalin) with alkyl aldehydes, followed by the Z-selective Horner-Wadsworth-Emmons (HWE) reaction and immediate lactonization, afforded γ-alkylated pentenolides in good overall yields and excellent
Enantioselective Syntheses of (–)-Alloyohimbane and (–)-Yohimbane by an Efficient Enzymatic Desymmetrization Process
Ghosh, Arun K.,Sarkar, Anindya
, p. 6001 - 6009 (2016/12/26)
Enantioselective syntheses of (–)-alloyohimbane and (–)-yohimbane were accomplished in a convergent manner. The key step involves a modified mild protocol for the enantioselective enzymatic desymmetrization of a meso-diacetate. This provides convenient access to an optically active monoacetate in multi-gram quantities and in high enantiomeric purity. This monoacetate was converted to (–)-alloyohimbane. Reductive amination of the derived aldehyde caused isomerization to the trans-product and, ultimately, the formation of (–)-yohimbane.
Rhodium-catalyzed hydrocarbonylation of a homoallylamine via n-h activation and application for synthesis of yohimbane alkaloids
Chiou, Wen-Hua,Wang, Yu-Wei,Kao, Chien-Lun,Chen, Po-Chou,Wu, Chen-Chang
, p. 4240 - 4244 (2014/11/26)
We describe syntheses of n-yohimbane and alloyohimbane using Rh-catalyzed hydrocarbonylation, which provides a practical methodology to synthesize a δ-lactam from a secondary homoallyl amine. We have also observed an unexpected transformation where the am
Aziridine-allylsilane-mediated total synthesis of (-)-yohimbane
Bergmeier, Stephen C.,Seth, Punit P.
, p. 3237 - 3243 (2007/10/03)
A total asymmetric synthesis of (-)-yohimbane and ent-alloyohimbane is reported. The synthesis utilizes a novel aziridine-allylsilane cyclization reaction as a key step in the synthesis. Treatment of optically pure aziridine-allylsilane 16 with BF3 · OEt2 provided a mixture of aminomethyl substituted carbocycles trans-20a and cis-20b in excellent yield and modest diastereoselectivity (trans/cis 3:1). Alkylation of the tosylamide followed by oxidation of the olefin in 20 provided the lactam 38, which was converted to (-)-yohimbane and ent-alloyohimbane by a Bischler-Napieralski reaction. The synthesis provided (-)-yohimbane in eight steps and 24% overall yield (from 16).
Symmetry-driven synthesis of indole alkaloids: Asymmetric total synthesis of (+)-yohimbine, (-)-yohimbone, (-)-yohimbane, and (+)-alloyohimbane
Aube,Ghosh,Tanol
, p. 9009 - 9018 (2007/10/02)
Total asymmetric syntheses of the target alkaloids are reported. The syntheses involve the preparation of enantiomerically pure (S,S)-1,3,3a,4,7,7a-hexahydro-2(H)-inden-2-one 7 and its meso isomer 5. Each ketone is then converted into a ring-expanded lactam using an oxaziridine synthesis/rearrangement protocol. The applications of Bischler-Napieralski ring constructions along with appropriate functional group transformations afford enantiomerically enriched alloyohimbane or yohimbane from the meso-or C2-symmetric ketones, respectively. A cis-5,6-diacetoxy compound (18) derived from the (S,S)-ketone served as the starting material for the total syntheses of the more highly functionalized alkaloids. Accordingly, a site-specific insertion of the indole-containing side chain was accomplished via stereoselective formation of an oxaziridine followed by its stereospecific rearrangement. The selectivity of this sequence allowed for the differentiation of alcohols at C-17 and C-18 (yohimbine numbering) and the synthesis of Δ18,19-yohimbone. This α,β-unsaturated ketone was converted into either (-)-yohimbone or (+)-yohimbine using standard chemistry.
Stereoselective Additions of Chiral α-Sulfinyl Ketimine Anions to Ene Esters. Asymmetric Syntheses of Indoloquinolizidine and Yohimban Alkaloids
Hua, Duy H.,Bharathi, S. Narasimha,Panangadan, Jagath A. K.,Tsujimoto, Atsuko
, p. 6998 - 7007 (2007/10/02)
The in-situ 1,4-addition/ring-closure reactions of chiral α-sulfinyl ketimine anions with acyclic and cyclic ene esters offer a simple, convenient route for the construction of chiral cyclic alkaloids having a nitrogen-atom ring juncture.Asymmetric induction in the conjugate-addition reaction of the carbanions derived from α-sulfinyl ketimines possessing chiral sulfur with various cyclic and acyclic ene esters, subsequent ring-closure reaction, and reduction of the resulting β-sulfinyl enamides were utilized in the syntheses of (-)-1,2,3,4,6,7,12,12b-octahydroindoloquinolizine , (-)-alloyohimban , (+)-3-epi-alloyohimban , and (-)-yohimban .
