Total syntheses of yohimbe alkaloids, with stereoselection for the normal, allo, and 3-epiallo series, based on annelations of 4-methoxy-1,2-dihydropyridones
摘要:
N-[2-(1H-3-indolyl)ethyl]-2,3-dihydro-4-pyridone (31) was generated in two steps (77% yield) from tryptamine and N-methyl-4-piperidone methiodide. Its cyclization (90% yield) and oxidation (91% yield) provided the tetracyclic analogue 32. O-Methylation and Robinson-type annelation of these vinylogous lactams (the latter in form of its N(a)-carbamate) furnished the dienones 38 (64%) and 43 (90%). Further elaboration by cyclization and/or reduction reactions selectively provided the 15,16-didehydroyohimbinones 7 or 44. Their reductions then led to yohimbinone (52, 20% overall yield from tryptamine), alloyohimbinone (11, 19% overall yield), and 3-epi-alloyohimbinone (10, 23% overall yield), which led to yohimbine (3), beta-yohimbine (9), 3-epi-alloyohimbine (53), and 3-epi-17-epi-alloyohimbine (54).
Expedient and Diastereodivergent Assembly of Terpenoid Decalin Subunits having Quaternary Stereocenters through Organocatalytic Robinson Annulation of Nazarov Reagent
report an expedient approach to highly functionalized cis‐ and trans‐decalines that could function as key structural subunits toward the synthesis of various classes of terpenoids. Key to the strategy is an organocatalyzed Robinsonannulation reaction of the Nazarovreagent that affords chiral enone building blocks with high enantioselectivities. The quaternary carbon stereogenic center can direct the subsequent
[EN] TOTAL SYNTHESIS OF ARTEMISININ<br/>[FR] SYNTHÈSE TOTALE D'ARTÉMISININE
申请人:UNIV INDIANA RES & TECH CORP
公开号:WO2012154906A1
公开(公告)日:2012-11-15
The present invention provides a method for manufacturing artemisinin and its congeners from cyclohexenone as a starting material.
本发明提供了一种从环己烯酮作为起始物质制造青蒿素及其同系物的方法。
A Three-Component Coupling Approach to Cyclopentanoids
作者:Barry M. Trost、Anthony B. Pinkerton
DOI:10.1021/jo010593b
日期:2001.11.1
A new approach to 2,3-disubstituted cyclopentenones has been developed. This approach consists of a two-step protocol involving the cyclization of a Z-vinyl bromide under Barbier type conditions to form a cyclopentenol, which is then oxidatively rearranged to generate the cyclopentenone. The Z-vinyl bromide is in turn derived from a ruthenium catalyzed three-component coupling of an alkyne, an enone
Bismuth Triflate-Catalyzed Addition of Allylsilanes to N-Alkoxycarbonylamino Sulfones: Convenient Access to 3-Cbz-Protected Cyclohexenylamines
作者:Thierry Ollevier、Zhiya Li
DOI:10.1002/adsc.200900710
日期:2009.12
Bismuth triflate was found to be an efficient catalyst in the Sakurai reaction of allyltrimethylsilanes with N-alkoxycarbonylaminosulfones. The reaction proceeded smoothly with a low catalyst loading of Bi(OTf)3⋅4 H2O (2–5 mol%) to afford the corresponding protected homoallylic amines in very good yields (up to 96%). A sequential allylation reaction followed by ring-closing metathesis delivers 6–8
Enantioselective Annulation Using Nazarov Reagent: Synthesis of (+)-Preoleanatetraene
作者:Alejandro F. Barrero、Simeón Arseniyadis、José F. Moral、M. Mar Herrador、Antonio Rosellón
DOI:10.1055/s-2005-864798
日期:——
The enantioselective synthesis of preoleanatetraene (1) has been accomplished via a convergent approach of two C-15 synthons. The key step of this synthesis has been an interesting enantioselective variant of the Robinson annulation using the Nazarov reagent and a chiral enamine to obtain the bicyclic moiety A. This asymmetric methodology opens the access to other irregular triterpene skeletons whose biogenetic implication should not be underestimated.