共查询到20条相似文献,搜索用时 15 毫秒
1.
[reaction: see text] A stereocontrolled approach for the preparation of the Danishefsky intermediates has been developed starting with the azaspirobicyclic ketone as a common precursor, representing a formal total synthesis of (+/-)-halichlorine and (+/-)-pinnaic acid. This approach involves the construction of the 1,7-disubstituted 6-azaspiro[4.5]decane with the proper stereochemistry established by olefin hydrogenation followed by C-methylation of the spirotricyclic lactam and the subsequent processes involving lactam ring-opening using methyl triflate and RCM to form the azaspirotricyclic quinolizidine skeleton. 相似文献
2.
A four-step stereocontrolled synthesis of polyfunctionalized cis-decalins is described, involving oxidation of 2-methoxyphenol, intermolecular Diels-Alder reaction, olefination, and Cope rearrangement. Application of this efficient strategy to the total syntheses of (+/-)-eremopetasidione, (+/-)-3 beta-angeloyloxyfuranoeremophilane, and (+/-)-3 beta-methacryloyloxyfuranoeremophilane was accomplished from creosol and ethyl vinyl ketone via a common intermediate 21. 相似文献
3.
An intramolecular hydroxy epoxide opening was used to access the cyclopenta[b]benzofuran ring system of the natural product rocaglaol (2). Our route allowed the stereocontrolled preparation of the rocaglaol derivative (+/-)-(1S*,3S*,3aR*,8bS*)-3b. The synthesis of the (+/-)-(3R*)-epimer of 3b was also achieved. Our strategy is well-suited for the production of analogues with variation of the western ring. [reaction: see text] 相似文献
4.
[reaction: see text] A highly efficient total synthesis of (+/-)-Lycoricidine is described. The synthesis features the ready preparation of the Lycoricidine skeleton by a Stille-IMDAF cycloaddition cascade. The resulting cycloadduct is then used for the stereocontrolled installation of the other functionality present in the C-ring of the target molecule. 相似文献
5.
The first synthesis of (+/-)-taxifolial A and iso-caulerpenyne was accomplished. The key steps in the sequence are (1) the stereoselective assembly of a vinyltin derived from butynediol and a functionalized aldehyde and (2) the construction of the dienyne moiety via a Stille cross-coupling. 相似文献
6.
Norcross NR Melbardis JP Solera MF Sephton MA Kilner C Zakharov LN Astles PC Warriner SL Blakemore PR 《The Journal of organic chemistry》2008,73(20):7939-7951
The three title alkaloids were separately prepared in stereocontrolled fashion from a common tetraoxobispidine precursor, 3,7-diallyl-2,4,6,8-tetraoxo-3,7-diazabicyclo[3.3.1]nonane (16). Bisimide 16 was generated from malonate via acid promoted cyclization of the Knoevenagel condensation adduct 1,1,3,3-propanetetracarboxamide. (+/-)-alpha-Isosparteine (dl-2) was elaborated from 16 in 28% overall yield by a two-directional synthetic sequence composed of four reactions: double addition of allylmagnesium bromide, ring-closing olefin metathesis (RCM), hydrogenation, and borane mediated reduction. (+/-)-beta-Isosparteine (dl-3) was targeted along similar lines by a strategic reversal in allylation and reduction operations on the core synthon. Thus, 16 was advanced to dl-3 in five steps and 12% overall yield by a reaction sequence commencing with sodium borohydride mediated reduction and followed by double Sakurai-type allylation of the resulting bishemiaminal. The synthesis of dl-3 was concluded by RCM and then global reduction (H2, Pd/C; LiAlH4). The final target, (+/-)-sparteine (dl-1), was secured in six steps and 11% overall yield from 16 by monoreduction and Sakurai allylation, followed by allyl Grignard addition and then RCM and global reduction as before. Reasons for the inherent C2-type regioselectivity of net double nucleophilic additions to tetraoxobispidines are discussed and enantioselective oxazaborolidine mediated reduction of the N,N'-dibenzyl congener of 16 is reported. 相似文献
7.
Majetich G Hicks R Zhang Y Tian X Feltman TL Fang J Duncan S 《The Journal of organic chemistry》1996,61(23):8169-8185
Concise syntheses of five tricyclic diterpenoids are reported. The key reaction in each synthesis is a cyclialkylation of a functionalized arene with a Lewis acid-activated conjugated dienone to generate a 6,7,6-fused tricycle. 相似文献
8.
[formula: see text] A regio- and stereospecific total synthesis of (+/-)-methyl rishirilide B (2b), and (alpha)2-macroglobulin inhibitor, is described. A key feature of the synthetic plan was regiospecific construction of a hydroanthracenone intermediate through condensation of a phenylsulfonyl isobenzofuranone with a functionalized 2-cyclohexen-1-one. Introduction of the vicinal trans-hydroxyl groups in the densely functionalized A-ring was accomplished via a novel one-pot procedure that involved oxidation of enolate anions with the Davis reagent. 相似文献
9.
[reaction: see text] A stereocontrolled total synthesis of (-)-kainic acid is described. A fully functionalized trisubstituted pyrrolidine ring was constructed by ring-closing metathesis of an acrylate derivative followed by an intramolecular Michael addition of the resultant alpha,beta-unsaturated lactone with high diastereoselectivity. Two alternative protocols for the construction of the alpha,beta-unsaturated lactone were also developed. 相似文献
10.
Sato K Akai S Sugita N Ohsawa T Kogure T Shoji H Yoshimura J 《The Journal of organic chemistry》2005,70(19):7496-7504
[reactions: see text] The novel and stereocontrolled synthesis of (+/-)-tetrodotoxin from myo-inositol is described. The key steps involve the stepwise oxidation of hydroxyl groups to the carbonyl function, followed by the addition of specific nucleophiles, including the successive spiro alpha-chloroepoxide formation and its ring-opening with the azide anion, to give the desired branched chain structures (5-->6, 17-->18-->19-->20 and 23-->24-->25) with the desired regio- and stereoselectivities in high yields. The stepwise conversion of the alpha-azido aldehyde 25 to the delta-lactone 29, followed by reduction of the azide, introduction of a guanidine moiety, aldehyde formation, and deprotection, produced the (+/-)-tetrodotoxin. 相似文献
11.
[structure: see text] A novel method for the stereocontrolled construction of the eudesmane ring system based on a cationic cyclization is presented, and the approach is exemplified in a short and efficient total synthesis of (+/-)-balanitol (2). 相似文献
12.
Reddy DS 《Organic letters》2004,6(19):3345-3347
[reaction: see text] An efficient, general, and fully stereocontrolled approach to the family of bakkanes is disclosed. This route highlights a highly diastereoselective Diels-Alder/aldol sequence to furnish the common hydrindane precursor for the synthesis of bakkanes. The projected common intermediate was transformed to the (+/-)-bakkenolide-A in a short sequence. 相似文献
13.
[reaction: see text] A convenient method for the preparation of 2,5-dihydrofurans by using the chemistry of alkynyl(phenyl)iodonium salts is reported. Treatment of 3-alkoxy-1-alkynyl(phenyl)iodonium triflates with sodium benzenesulfinate generates an alkylidenecarbene, which undergoes [1,5]-C-H insertion to form 2-substituted 4-benzenesulfonyl-2,5-dihydrofurans in reasonable yield. These cyclic vinyl sulfones are functionalized in such a way as to make them useful starting materials for the preparation of lignans. The application of this methodology to the first total synthesis of (+/-)-magnofargesin is disclosed. 相似文献
14.
[reaction: see text] A stereocontrolled route to Nuphar alkaloids is described that employs a formal [3 + 3] cycloaddition strategy to assemble the piperidine nucleus. The addition of Pd-TMM complexes to aziridine 10 was found to be sluggish; however, the addition of a functionalized allyl Grignard reagent followed by a Mitsunobu condensation reaction provided 11 in high yield. The employment of this route in the formal synthesis of (-)-deoxynupharidine 1 is described. 相似文献
15.
[process--see text] The total synthesis of (+/-)-sarcodonin G (3), a highly functionalized member of the cyathane family of diterpenoids, is described. 相似文献
16.
The total synthesis of kalihinol C, a bis-isonitrile marine diterpenoid isolated from Acanthella sp., is reported. The decalin framework was established via an intramolecular Diels-Alder cycloaddition and subsequently functionalized through a series of substrate-controlled diastereoselective transformations to install the tertiary isonitrile, beta-hydroxy isonitrile, and pendant tetrahydrofuranyl ring. 相似文献
17.
[reaction: see text] A chemo- and stereoselective palladium-catalyzed amination of silylated butenediol dicarbonates has allowed for the introduction of a glycine moiety to obtain a desired functionalized epoxysilane. A stereoselective aldolization then delivered the piperidine ring which may be used as a precursor for the synthesis of a variety of polyhydroxylated azasugars. This efficient approach has been illustrated by the synthesis of 1-deoxymannojirimycin including a stereoselective reduction with LAH and a Tamao-Fleming oxidation of a C-SiMe(2)Ph bond. 相似文献
18.
[structure: see text] The total synthesis of (-)-21-isopentenylpaxilline (1) has been achieved. Key elements of the synthesis include the stereocontrolled construction of the advanced eastern hemisphere (-)-5, a highly efficient union of the eastern and western fragments (-)-5 and 4, respectively, exploiting our 2-substituted indole synthesis, and a new protocol for the construction of ring C. 相似文献
19.
A new method which is based on (2-3)-Wittig sigmatropic rearrangements for the stereocontrolled synthesis of functionalized three-carbon side chains on the basic tetracyclic steroidal system is described. 相似文献
20.
T Ling C Chowdhury B A Kramer B G Vong M A Palladino E A Theodorakis 《The Journal of organic chemistry》2001,66(26):8843-8853
An enantioselective synthesis of the potent antiinflammatory agent (-)-acanthoic acid (1) is described. The successful strategy departs from (-)-Wieland-Miescher ketone (10), which is readily available in both enantiomeric forms and constitutes the starting point toward a fully functionalized AB ring system of 1. Conditions were developed for a regioselective double alkylation at the C4 center of the A ring, which produced compound 32 as a single stereoisomer. Construction of the C ring of 1 was accomplished via a Diels-Alder reaction between sulfur-containing diene 43 and methacrolein (36), which after desulfurization and further functionalization yielded synthetic acanthoic acid. The described synthesis confirms the proposed stereochemistry of the natural product and represents a fully stereocontrolled entry into an underexplored class of biologically active diterpenes. 相似文献