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1.
Treatment of (aR)‐[1,1′binaphthalene]‐8,8′‐diol ((−)‐ 1 ) with hexamethylphosphorous triamide afforded the N,N‐dimethylphosphoramidite (−)‐ 3 (Scheme 1). The synthesis of the analogous N,N‐diisopropylphosphoramidite 4 failed, however, and afforded the acyclic phosphonamidate (−)‐ 5 . The application of the cyclic phosphoramidite (−)‐ 3 towards asymmetric catalysis was investigated. The borane reduction of acetophenone ( 6 ) to (R)‐1‐phenylethanol ( 7 ) in the presence of (−)‐ 3 proceeded with 96% ee (Scheme 2). The use of (−)‐ 3 as ligand in several Cu‐catalyzed addition and substitution reactions resulted in enantioselectivities ranging from 0 to 50% (Schemes 3 and 4). 相似文献
2.
Richard Detterbeck Armin Guggisberg Kasim Popaj Manfred Hesse 《Helvetica chimica acta》2002,85(6):1742-1758
(−)‐(3S)‐3‐(Tosylamino)butano‐4‐lactone ( 1 ) and its derivative ethyl (−)‐(3S)‐4‐iodo‐3‐(tosylamino)butanoate ( 2 ) are presented as easily accessible chiral building blocks for the construction of a range of different macrolactam frameworks important for the synthesis of naturally occurring polyamine alkaloids as well as for establishing a substance library of such compounds, including S‐containing derivatives for biological tests. In addition to that, the absolute configuration of the spermine alkaloid (−)‐(R)‐budmunchiamine A ( 3 ) from Albizia amara was determined by total synthesis according to the new methodology. 相似文献
3.
Beau P. Pritchett Jun Kikuchi Yoshitaka Numajiri Brian M. Stoltz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(43):13727-13730
The successful application of dihydropyrido[1,2‐a]indolone (DHPI) substrates in Pd‐catalyzed asymmetric allylic alkylation chemistry facilitates rapid access to multiple alkaloid frameworks in an enantioselective fashion. Strategic bromination at the indole C3 position greatly improved the allylic alkylation chemistry and enabled a highly efficient Negishi cross‐coupling downstream. The first catalytic enantioselective total synthesis of (−)‐goniomitine, along with divergent formal syntheses of (+)‐aspidospermidine and (−)‐quebrachamine, are reported herein. 相似文献
4.
The synthesis of enantiomerically pure (+)‐ and (−)‐γ‐ionone 3 is reported. The first step in the synthesis is the diastereoisomeric enrichment of 4‐nitrobenzoate derivatives of racemic γ‐ionol 12 . The enantioselective lipase‐mediated kinetic acetylation of γ‐ionol 13b afforded the acetate 14 and the alcohol 15 , which are suitable precursors of the desired products (−)‐ and (+)‐ 3 , respectively. The olfactory evaluation of the γ‐ionone isomers shows a great difference between the two enantiomers both in fragrance response and in detection threshold. The selective reduction of (−)‐ 3 and (+)‐ 3 to the γ‐dihydroionones (−)‐(R)‐ 16 and (+)‐(S)‐ 17 , respectively, allowed us to assign unambiguously the absolute configuration of the γ‐ionones. 相似文献
5.
《化学:亚洲杂志》2017,12(12):1309-1313
An asymmetric route to (−)‐α‐lycorane and (−)‐zephyranthine, and a formal total synthesis of (+)‐clivonine were achieved. A pivotal intermediate, which serves as a potent precursor for the divergent syntheses of these natural products, was accessed by a diastereoselective Pd‐catalyzed cinnamylation of an N ‐tert ‐butanesulfinyl imine. 相似文献
6.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(1):330-333
The first enantioselective total synthesis of (−)‐cycloclavine was accomplished in 8 steps and 7.1 % overall yield. Key features include the first catalytic asymmetric cyclopropanation of allene, mediated by the dirhodium catalyst Rh2(S‐TBPTTL)4, and the enone 1,2‐addition of a new TEMPO carbamate methyl carbanion. An intramolecular strain‐promoted Diels–Alder methylenecyclopropane (IMDAMC) reaction provided a pivotal tricyclic enone intermediate with more than 99 % ee after crystallization. The synthesis of (−)‐ 1 was completed by a late‐stage intramolecular Diels–Alder furan (IMDAF) cycloaddition to install the indole. 相似文献
7.
Delphine Josien‐Lefebvre Guillaume Desmares ClaudeLe Drian 《Helvetica chimica acta》2001,84(4):890-897
The total synthesis of the naturally occurring cyanoglucoside (−)‐bauhinin ( 1 ) was achieved starting from the optically pure oxatrinorbornenone 2 in 12 steps and 8% overall yield. The aglycone of (−)‐bauhinin was easily obtained from the optically pure oxatrinorbornenone derivative 6 by a Wittig‐Horner reaction followed by the opening of the oxa bridge. Glycosidation with tetra‐O‐isobutyryl‐D ‐glucosyl bromide 9 as the reagent in the Koenigs‐Knorr reaction afforded glucoside 10 in 58% yield, which, after photoisomerization and deprotection, gave (−)‐bauhinin ( 1 ). 相似文献
8.
Andrea Brecht‐Forster Juliette Fitremann Philippe Renaud 《Helvetica chimica acta》2002,85(11):3965-3974
The formal syntheses of (±)‐nephromopsinic acid, (−)‐phaseolinic acid, and the first total synthesis of (−)‐dihydropertusaric acid from (±)‐ and (−)‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐one are described. These syntheses take advantage of a previously reported radical rearrangement (1,2‐acyl migration). A remarkable iodide‐mediated cleavage of a bicyclic system, followed by the introduction of the γ‐chains via a mixed Kolbe electrolysis, are the key steps of these syntheses. This approach is general and could be applied for the preparation of all kinds of paraconic acids with excellent control of the stereochemistry. 相似文献
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(44):14021-14025
The first total synthesis of the 2,3,5‐O ‐(S ,R )‐nonahydroxytriphenoylated (NHTP) C ‐glucosidic ellagitannin (−)‐vescalin was accomplished through a series of transformations mimicking the sequence of events leading to its biogenesis. The key steps of this synthesis encompass a Wittig‐mediated ring opening of a glucopyranosic hemiacetal, a C‐glucosidation event through a phenolic aldol‐type reaction, and a Wynberg–Feringa–Yamada‐type oxidative phenolic coupling, which forged the NHTP unit of (−)‐vescalin. 相似文献
10.
TeresaB. Freedman RinaK. Dukor PeterJ.C.M. vanHoof EdwinR. Kellenbach LaurenceA. Nafie 《Helvetica chimica acta》2002,85(4):1160-1165
The absolute configuration of the (−)‐enantiomer of mirtazapine was determined by means of vibrational circular dichroism (VCD). The observed VCD of (−)‐mirtazapine showed excellent correlation with the calculated VCD of the (R)‐enantiomer. This is in agreement with the absolute configuration as determined by independent synthesis starting from (R)‐phenylglycine. 相似文献
11.
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
12.
Ronald Nelson Moiss Gulías Jos L. Mascareas Fernando Lpez 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(46):14571-14575
A practical synthesis of (−)‐englerin A was accomplished in 17 steps and 11 % global yield from commercially available achiral precursors. The key step consists of a platinum‐catalyzed [4C+3C] allenediene cycloaddition that directly delivers the trans‐fused guaiane skeleton with complete diastereoselectivity. The high enantioselectivity (99 % ee) stems from an asymmetric ruthenium‐catalyzed transfer hydrogenation of a readily assembled diene–ynone. The synthesis also features a highly stereoselective oxygenation, and a late‐stage cuprate alkylation that enables the preparation of previously inaccessible structural analogues. 相似文献
13.
Elisabetta Brenna Marco Delmonte Claudio Fuganti Stefano Serra 《Helvetica chimica acta》2001,84(1):69-86
The (−)‐ and (+)‐β‐irones ((−)‐ and (+)‐ 2 , resp.), contaminated with ca. 7 – 9% of the (+)‐ and (−)‐trans‐α‐isomer, respectively, were obtained from racemic α‐irone via the 2,6‐trans‐epoxide (±)‐ 4 (Scheme 2). Relevant steps in the sequence were the LiAlH4 reduction of the latter, to provide the diastereoisomeric‐4,5‐dihydro‐5‐hydroxy‐trans‐α‐irols (±)‐ 6 and (±)‐ 7 , resolved into the enantiomers by lipase‐PS‐mediated acetylation with vinyl acetate. The enantiomerically pure allylic acetate esters (+)‐ and (−)‐ 8 and (+)‐ and (−)‐ 9 , upon treatment with POCl3/pyridine, were converted to the β‐irol acetate derivatives (+)‐ and (−)‐ 10 , and (+)‐ and (−)‐ 11 , respectively, eventually providing the desired ketones (+)‐ and (−)‐ 2 by base hydrolysis and MnO2 oxidation. The 2,6‐cis‐epoxide (±)‐ 5 provided the 4,5‐dihydro‐4‐hydroxy‐cis‐α‐irols (±)‐ 13 and (±)‐ 14 in a 3 : 1 mixture with the isomeric 5‐hydroxy derivatives (±)‐ 15 and (±)‐ 16 on hydride treatment (Scheme 1). The POCl3/pyridine treatment of the enantiomerically pure allylic acetate esters, obtained by enzymic resolution of (±)‐ 13 and (±)‐ 14 , provided enantiomerically pure cis‐α‐irol acetate esters, from which ketones (+)‐ and (−)‐ 22 were prepared (Scheme 4). The same materials were obtained from the (9S) alcohols (+)‐ 13 and (−)‐ 14 , treated first with MnO2, then with POCl3/pyridine (Scheme 4). Conversely, the dehydration with POCl3/pyridine of the enantiomerically pure 2,6‐cis‐5‐hydroxy derivatives obtained from (±)‐ 15 and (±)‐ 16 gave rise to a mixture in which the γ‐irol acetates 25a and 25b and 26a and 26b prevailed over the α‐ and β‐isomers (Scheme 5). The (+)‐ and (−)‐cis‐γ‐irones ((+)‐ and (−)‐ 3 , resp.) were obtained from the latter mixture by a sequence involving as the key step the photochemical isomerization of the α‐double bond to the γ‐double bond. External panel olfactory evaluation assigned to (+)‐β‐irone ((+)‐ 2 ) and to (−)‐cis‐γ‐irone ((−)‐ 3 ) the strongest character and the possibility to be used as dry‐down note. 相似文献
14.
Lenka Nezbedov Konstantin Drandarov Christa Werner Manfred Hesse 《Helvetica chimica acta》2000,83(11):2953-2960
The asymmetric synthesis of the unlabeled and [D8]‐labeled terminal precursors, 4 ((−)‐(S)‐dihydroxyverbacine) and 19 , respectively, in the biogenesis of the spermine alkaloids aphelandrine ( 5 ) and orantine ( 6 ), respectively, is described. A partial synthesis of the alkaloid (−)‐(S)‐[(E)‐4‐methoxycinnamoyl]buchnerine ( 10 ) is also presented. 相似文献
15.
The cyclic [2R,S(R)]‐bornane‐10,2‐sulfinamide (−)‐ 2b , an analogue of Oppolzer`s camphor‐derived sultam (−)‐ 2a , was synthesized by reduction of the known N‐alkylidenesulfinamide (+)‐ 1b with NaBH4. The uncatalyzed [4+2] cycloaddition of cyclopentadiene to the methyl ester (−)‐ 3b of the N‐fumaroylsulfinamide, obtained from (−)‐ 2b , proceeds with lower endo and π‐facial selectivity as compared to dienophiles (−)‐ 3a , c . In contrast to these latter, the diastereoselectivity is reversed either in apolar CCl4 or in the presence of TiCl4. This inversion is explained by a competitive C(α)‐si addition on the reactive anti‐s‐trans conformer. 相似文献
16.
Cedric L. Hugelshofer Thomas Magauer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(42):11533-11537
The first asymmetric total synthesis of the antifeedant terpenoids (+)‐norleucosceptroid A, (−)‐norleucosceptroid B, and (−)‐leucosceptroid K has been accomplished. This highly concise synthetic route was guided by our efforts to develop a platform for the collective synthesis of a whole family of antifeedant natural products. The synthesis features a Hauser–Kraus‐type annulation followed by an unprecedented, highly efficient intramolecular dilactol aldol‐type condensation reaction to produce the 5,6,5 skeleton. The developed synthetic route proceeds for norleucosceptroid A and B in 16 steps (longest linear sequence) from known compounds. 相似文献
17.
Haruhiko Fuwa Yuta Okuaki Naoya Yamagata Makoto Sasaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(3):882-887
(−)‐Lyngbyaloside B is a 14‐membered macrolide glycoside isolated from the marine cyanobacterium Lyngbya sp. as a cytotoxic substance by Moore and co‐workers. The first total synthesis of (−)‐lyngbyaloside B and the reassignment of its stereostructure is described. The synthesis features an Abiko–Masamune aldol reaction, a vinylogous Mukaiyama aldol reaction, and a macrocyclization involving an acyl ketene intermediate for the construction of the macrocyclic backbone, which contains an acylated tertiary alcohol. The antiproliferative activity of selected compounds against a small panel of human cancer cell lines is also reported. 相似文献
18.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(46):14855-14858
One of a number of intriguing new alkaloids isolated from the Leucetta sp. sponge in 2004, spiroleucettadine displayed unique structural features on a restricted scaffold: a trans ‐fused 5,5‐bicyclic ring system together with an amino hemiketal moiety. Attempts to synthesize the initially proposed structure failed, raising questions as to its veracity, and structure revision ensued in 2008; no successful synthetic approach has been reported to date. Herein, we describe the enantiospecific total synthesis of (−)‐spiroleucettadine by a highly efficient biomimetic approach starting from l ‐tyrosine. One of two key hypervalent‐iodine‐mediated oxidation reactions forged the spirocyclic center, and the other enabled the installation of the methylamine side chain in the penultimate step. Our approach provides synthetic access to a new class of spiroannulated natural products and will enable future studies of the structure–biological‐activity relationships of these antibacterial compounds. 相似文献
19.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(44):14045-14048
The first enantioselective total synthesis of (−)‐deoxoapodine is described. Our synthesis of this hexacyclic aspidosperma alkaloid includes an efficient molybdenum‐catalyzed enantioselective ring‐closing metathesis reaction for the desymmetrization of an advanced intermediate that introduces the C5‐quaternary stereocenter. After C21‐oxygenation, the pentacyclic core was accessed by electrophilic C19‐amide activation and transannular spirocyclization. A biogenetically inspired dehydrative C6‐etherification reaction proved highly effective to secure the F‐ring and the fourth contiguous stereocenter of (−)‐deoxoapodine with complete stereochemical control. 相似文献
20.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(6):1571-1574
The enantioselective total synthesis of (−)‐tetrodotoxin [(−)‐TTX] and 4,9‐anhydrotetrodotoxin, which are selective blockers of voltage‐gated sodium channels, was accomplished from the commercially available p ‐benzoquinone. This synthesis was based on efficient stereocontrol of the six contiguous stereogenic centers on the core cyclohexane ring through Ogasawara's method, [3,3]‐sigmatropic rearrangement of an allylic cyanate, and intramolecular 1,3‐dipolar cycloaddition of a nitrile oxide. Our synthetic route was applied to the synthesis of the tetrodotoxin congeners 11‐norTTX‐6(R )‐ol and 4,9‐anhydro‐11‐norTTX‐6(R )‐ol through late‐stage modification of the common intermediate. Neutral deprotection at the final step enabled easy purification of tetrodotoxin and 11‐norTTX‐6(R )‐ol without competing dehydration to their 4,9‐anhydro forms. 相似文献