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1.
The first total synthesis of the natural product (?)‐(19R)‐ibogamin‐19‐ol ((?)‐ 1 ) is reported (biogenetic atom numbering). Starting with L ‐glutamic acid from the chiral pool and (2S)‐but‐3‐en‐2‐ol, the crucial aliphatic isoquinuclidine (= 2‐azabicyclo[2.2.2]octane) core containing the entire configurational information of the final target was prepared in 15 steps (overall yield: 15%). The two key steps involved a highly effective, self‐immolating chirality transfer in an Ireland–Claisen rearrangement and an intramolecular nitrone‐olefin 1,3‐dipolar cycloaddition reaction (Scheme 3). Onto this aliphatic core was grafted the aromatic moiety in the form of N(1)‐protected 1H‐indole‐3‐acetic acid by application of the dicyclohexylcarbodiimide (DCC) method (Scheme 4). Four additional steps were required to adjust the substitution pattern at C(16) and to deprotect the indole subunit for the closure of the crucial 7‐membered ring present in the targeted alkaloid family (Schemes 4 and 5). The spectral and chiroptical properties of the final product (?)‐ 1 matched the ones reported for the naturally occurring alkaloid, which had been isolated from Tabernaemonatana quadrangularis in 1980. The overall yield of the entire synthesis involving a linear string of 20 steps amounted to 1.9% (average yield per step: 82%). 相似文献
2.
Guan‐Sai Liu Yuan‐Shan Yao Peng Xu Shaozhong Wang Dr. Zhu‐Jun Yao Prof. Dr. 《化学:亚洲杂志》2010,5(6):1382-1388
An efficient total synthesis of (S)‐14‐azacamptothecin has been accomplished in 10 steps and 56 % overall yield from 5H‐pyrano[4,3‐d]pyrimidine 8 . A mild Hendrickson reagent‐triggered intramolecular cascade cyclization, a highly enantioselective dihydroxylation, and an efficient palladium‐catalyzed transformation of an O‐allyl into N‐allyl group are the key steps in the synthesis. This work provides a much higher overall yield than the previous achievement and shows sound flexibility for the further applications that will lead to new bioactive analogues. 相似文献
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4.
An Efficient Stereoselective Total Synthesis of Bioactive (3R,5R)‐1‐(4‐Hydroxyphenyl)‐7‐phenylheptane‐3,5‐diol via Asymmetric Aldol Reaction 下载免费PDF全文
An efficient stereoselective total synthesis of (3R,5R)‐1‐(4‐hydroxyphenyl)‐7‐phenylheptane‐3,5‐diol ( 1 ) is reported based on the Mukaiyama aldol reaction. The total synthesis of compound 1 was accomplished with 30% overall yield in simple eight steps from commercially available trans‐cinnamaldehyde. 相似文献
5.
Eric E. Boros Istvan Kaldor Philip S. Turnbull 《Journal of heterocyclic chemistry》2011,48(3):733-736
2‐Methyl‐4‐(trifluoromethyl)‐1H‐indole‐5‐carbonitrile is a key intermediate in the synthesis of selective androgen receptor modulators discovered in these laboratories. A practical and convergent synthesis of the title compound starting from 4‐nitro‐3‐(trifluoromethyl)phenol and tert‐butyl acetoacetate was developed, including a telescoped procedure for synthesis (without isolation) and Nenitzescu reaction of 2‐trifluoromethyl‐1,4‐benzoquinone. Conversion of the known Nenitzescu indole product to a novel triflate intermediate followed by palladium‐catalyzed cyanation afforded a penultimate carbonitrile. Removal of the C‐3 tert‐butyl ester group on the indole through a decarboxylative pathway completed the synthesis of the title compound in six steps (27% overall yield) from 4‐nitro‐3‐(trifluoromethyl)phenol (five steps, 37% overall yield from tert‐butyl acetoacetate). J. Heterocyclic Chem., (2011). 相似文献
6.
Tiziana Benincori Silvana Bruno Giuseppe Celentano Tullio Pilati Alessandro Ponti Simona Rizzo Mara Sada Francesco Sannicol 《Helvetica chimica acta》2005,88(7):1776-1789
A process‐scale stereoselective synthesis of nature‐identical (−)‐(S,S)‐7‐hydroxycalamenal (=(−)‐(5S,8S)‐5,6,7,8‐tetrahydro‐3‐hydroxy‐5‐methyl‐8‐(1‐methylethyl)naphthalene‐2‐carbaldehyde; (−)‐ 1a ) in 96% enantiomeric excess (ee) with the aid of chiral Ru complexes has been developed. The key step was the enantioselective hydrogenation of easily accessible 2‐(4‐methoxyphenyl)‐3‐methylbut‐2‐enoic acid ( 10 ) to (+)‐ 11 in a 86% ee (Scheme 5 and Table 1). A substantial increase in optical purity (96% ee) was achieved by induced crystallization of the intermediate (+)‐3,4‐dihydro‐4‐(1‐methylethyl)‐7‐methoxy‐2H‐naphthalen‐1‐one ((+)‐ 3 ). Computational conformation analysis carried out on the analog (−)‐ 9 rationalized the high diastereoselectivity achieved in the catalytic hydrogenation of the CC bond. 相似文献
7.
Stereoselective Total Synthesis of (3S,5S)‐1,7‐Bis(4‐hydroxyphenyl)heptane‐3,5‐diol, (3S,5S)‐Alpinikatin,and Its Diastereoisomers 下载免费PDF全文
Kunuru Venkatesham Sudina Purushotham Reddy Baggu Chinnababu Katragadda Suresh Babu 《Helvetica chimica acta》2015,98(9):1307-1314
Stereoselective synthesis of the diarylheptanoids, (3S,5S)‐1,7‐bis(4‐hydroxyphenyl)heptane‐3,5‐diol ( 1 ), (3S,5S)‐alpinikatin ( 3 ), and their diastereoisomers ( 2 and 4 , resp.), was achieved from readily available 4‐hydroxybenzaldehyde. The synthetic sequences involve Browns's allylation and Et2Zn mediated diastereoselective alkynylation reaction as key steps. 相似文献
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An enantioselective synthesis of (+)‐β‐himachalene ( 2 ) was accomplished starting from (1S,2R)‐1,2‐epoxy‐p‐menth‐8‐ene ( 3 ) in 15 or 16 steps with an overall yield of ca. 6% (Schemes 3, 5, and 6). Key transformations include an Ireland–Claisen rearrangement, a Corey oxidative cyclization, and a ring expansion. 相似文献
10.
Jianmin Shi Liang Wei Lu Liu Meng Tang Tao Zhang Hongjin Bai Zhenting Du 《中国化学会会志》2019,66(7):756-760
An asymmetric synthesis of (4R,8R)‐4,8‐dimethyldecanal, the most active component of natural tribolure, was achieved through an asymmetric methylation as a key step and chiral‐pool strategy. Natural tribolure is a mixture of four stereoisomers, (4R,8R)/(4R,8S)/(4S,8R)/(4S,8S), and their ratio is 4/4/1/1. However, the (4R,8R)‐isomer is the most active one. Based on a chiral‐pool strategy, we used a recycled chiral molecular (R)‐4‐(Benzyloxy)‐3‐methylbutanal that we exploited in our previous article. After executing a C5 + C5 + C2 synthetic plan, the target molecule was obtained in nine linear steps and in 36.8% overall yield. 相似文献
11.
Parigi Raghavendar Reddy Chithaluri Sudhakar Jayprakash Narayan Kumar Biswanath Das 《Helvetica chimica acta》2013,96(2):289-295
The first stereoselective total synthesis of the naturally occurring anti‐emetic diarylheptanoid (3R,5R)‐1‐(4‐hydroxyphenyl)‐7‐phenylheptane‐3,5‐diol ( 1 ) was accomplished starting from 4‐hydroxybenzaldehyde and involving a Sharpless kinetic resolution and an asymmetric epoxidation as the key steps (Scheme 2). The enantiomer 1a of this compound was also simultaneously prepared. 相似文献
12.
Meruva Suresh Babu Akula Raghunadh Konda Ramulu Vilas H. Dahanukar Unniaran K. Syam Kumar P. Kumar Dubey 《Helvetica chimica acta》2014,97(11):1507-1515
A highly enantiospecific, azide‐free synthesis of (?)‐(R)‐ and (+)‐(S)‐piperidin‐3‐ol in excellent yield was developed. The key step of the synthesis involves the enantiospecific ring openings of enantiomerically pure (R)‐ and (S)‐2‐(oxiran‐2‐ylmethyl)‐1H‐isoindole‐1,3(2H)‐diones with the diethyl malonate anion and subsequent decarboxylation. 相似文献
13.
The Use of Pinner Type Reaction for the Synthesis of New Indeno[2,1‐c]pyridine‐4‐carbonitrile Derivatives 下载免费PDF全文
Prashant S. Nikam Shivaraj P. Patil Shrikant B. Kanawade Sachin A. Gangurde Meenakshi Rathi Raghunath B. Toche 《Journal of heterocyclic chemistry》2015,52(1):150-155
An efficient and convenient route was developed for the synthesis of new pyridinecarbonitrile derivatives by using the Pinner type of reaction. The 2‐((E)‐2‐((dimethylamino)methylene)‐1,2‐dihydro‐5,6‐dimethoxyinden‐3‐ylidene) malononitrile 2 was reacted in the presence of dry HCl gas to yield 3‐chloro‐6,7‐dimethoxy‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitrile ( 3 ) in good yield. The SNAr reaction on compound 3 with various nucleophiles yielded 3‐substituted pyridinecarbonitriles 4 , 5 , 6 , 7 , 8 , 9 in moderate to good yield. 相似文献
14.
Enantiospecific Synthesis of (R)‐3‐Amino‐4‐(2,4,5‐trifluorophenyl)butanoic Acid Using (S)‐Serine as a Chiral Pool 下载免费PDF全文
Aytekin Köse Özlem Gündoğdu Derya Aktaş Meryem Fıstıkçı Ramazan Altundaş Hasan Seçen Yunus Kara 《Helvetica chimica acta》2015,98(2):260-266
Starting from (S)‐serine, a new method was developed for the synthesis of the β‐amino acid part of sitagliptin in ten steps and with an overall yield of 30%. The crucial step of the synthesis was the ring opening of N‐ and O‐protected (R)‐aziridin‐2‐methanol with (2,4,5‐trifluorophenyl)magnesium bromide to give N‐ and O‐protected (R)‐2‐amino‐3‐(2,4,5‐trifluorophenyl)propan‐1‐ol. 相似文献
15.
《Journal of heterocyclic chemistry》2017,54(4):2237-2241
A new and convenient synthesis of 7‐(3‐chloropropoxy)‐4‐hydroxy‐6‐methoxyquinoline‐3‐carbonitrile, the key intermediate to bosutinib, is described on a hectogram scale. 5‐Bromo‐2‐methoxyphenol is adopted as the starting material via the simple chemical process including Friedel‐Crafts reaction, alkylation, bromination, cyano substitution, and so on to give the 3‐amino‐2‐(2‐bromobenzoyl)acrylonitrile compound 25 , which underwent key intramolecular cyclization at K2CO3/DMF condition; the title product was obtained in 36.9% yield over 7 steps and 98.71% purity (HPLC). 相似文献
16.
Vishnumurthy R. Hegde Katherine L. Seley Stewart W. Schneller 《Journal of heterocyclic chemistry》2000,37(5):1361-1362
A preparation of (1′R,2′S,3′R,4′S)‐1‐(2′,3′,4′‐trihydroxycyclopent‐1′‐yl)‐lH‐cytosine (5′‐norcarbodine, 3 ) has formally been achieved in 2 steps from (+)‐(1R,4S)‐4‐hydroxy‐2‐cyclopenten‐1‐yl acetate ( 4 ) and cytosine. The L‐like enantiomer of 3 (that is, 6 ) is also reported using the enantiomer of 4 (that is, 7 ). In evalu ating 3 and 6 for antiviral potential against a number of viruses, compound 3 was found to have activity towards Epstein‐Barr virus (EBV). 相似文献
17.
Isopropylidene‐protected (S)‐4‐O‐(methylsulfonyl)butane‐1,2,4‐triol was used for alkylation of 5‐[(pyren‐3‐yl)methylidene]hydantoin to give the N3‐monoalkylated product 4 in 29% yield together with a dialkylated product 5 in 12% yield. After deprotection, compound 4 was transformed into a dimethoxytrityl (DMT)‐protected phosphoramidite building block 9 for standard DNA synthesis. When inserted as a bulge in the triplex‐forming oligomer, compound 6 stabilizes a DNA triplex, whereas the corresponding DNA/DNA and DNA/RNA duplexes are slightly destabilized. For the triplex, fluorescence enhancement was observed at 500 nm. 相似文献
18.
We describe the synthesis of (5′S)‐5′‐C‐butylthymidine ( 5a ), of the (5′S)‐5′‐C‐butyl‐ and the (5′S)‐5′‐C‐isopentyl derivatives 16a and 16b of 2′‐deoxy‐5‐methylcytidine, as well as of the corresponding cyanoethyl phosphoramidites 9a , b and 14a , b , respectively. Starting from thymidin‐5′‐al 1 , the alkyl chain at C(5′) is introduced via Wittig chemistry to selectively yield the (Z)‐olefin derivatives 3a and 3b (Scheme 2). The secondary OH function at C(5′) is then introduced by epoxidation followed by regioselective reduction of the epoxy derivatives 4a and 4b with diisobutylaluminium hydride. In the latter step, a kinetic resolution of the diastereoisomer mixture 4a and 4b occurs, yielding the alkylated nucleoside 2a and 2b , respectively, with (5′S)‐configuration in high diastereoisomer purity (de=94%). The corresponding 2′‐deoxy‐5‐methylcytidine derivatives are obtained from the protected 5′‐alkylated thymidine derivatives 7a and 7b via known base interconversion processes in excellent yields (Scheme 3). Application of the same strategy to the purine nucleoside 2′‐deoxyadenine to obtain 5′‐C‐butyl‐2′‐deoxyadenosine 25 proved to be difficult due to the sensitivity of the purine base to hydride‐based reducing agents (Scheme 4). 相似文献
19.
The hydrochlorides of both enantiomers of the antibiotic anisomycin were prepared starting with the ‘diacetone‐fructose’‐substituted allene 1 and the N‐Boc‐protected imine precursor 2a . Addition of an excess of lithiated 1 to 2a provided a 2 : 1 mixture 3a of diastereoisomers, which were cyclized to 4a under base promotion (Scheme 2). The two diastereoisomers of 4a were separated and converted into enantiomerically pure pyrrolidin‐3‐ones (2R)‐ 5a and (2S)‐ 5a . A similar sequence yielded the N‐Tos‐protected compounds (2R)‐ 5b and (2S)‐ 5b . Compounds 5a were converted into silyl enol ethers 6 and by subsequent regio‐ and stereoselective hydroboration into pyrrolidine derivatives 7 (Scheme 3). Straightforward functional‐group transformations led to the hydrochlorides 9 of anisomycin (Scheme 3). The (2R) series provided the hydrochloride (2R)‐ 9 of the natural occurring enantiomer, whereas the (2S) series furnished the antipode (2S)‐ 9 . The overall sequence to the natural product involved ten steps with eight purified intermediates and afforded an overall yield of 8%. Our stereochemically divergent approach to this type of hydroxylated pyrrolidines is highly flexible and should easily allow preparation of many analogues. 相似文献
20.
Marko kof Jurij Svete Branko Stanovnik Simona Goli
‐Grdadolnik 《Helvetica chimica acta》2000,83(4):760-766
(3E,5S)‐1‐Benzoyl‐5‐[(benzoyloxy)methyl]‐3‐[(dimethylamino)methylidene]pyrrolidin‐2‐one ( 9 ) was prepared in two steps from commercially available (S)‐5‐(hydroxymethyl)pyrrolidin‐2‐one ( 7 ) (Scheme 1). Compound 9 gave, in one step, upon treatment with various C,N‐ and C,O‐1,3‐dinucleophiles 10 – 18 , the corresponding 3‐(quinolizin‐3‐yl)‐ and 3‐(2‐oxo‐2H‐pyran‐3‐yl)‐substituted (2S)‐2‐(benzoylamino)propyl benzoates 19 – 27 (Schemes 1 and 2). 相似文献