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1.
Rodney A. Fernandes Mahesh B. Halle Asim K. Chowdhury Arun B. Ingle 《Tetrahedron: Asymmetry》2012,23(1):60-66
A diastereoselective synthesis of (+)-nephrosterinic acid and (+)-protolichesterinic acid, common members of the paraconic acids is described. The synthesis is based on a diastereoselective orthoester Johnson–Claisen rearrangement of a (Z)-allyl alcohol with a vicinal dioxolane moiety as key steps. The synthesis is completed in 10 steps and with overall yields of 15.9% for (+)-nephrosterinic acid and 16.4% for (+)-protolichesterinic acid. 相似文献
2.
(+)-Benzoylselenopederic acid (1), a left half of (+)-pederin (3), was synthesized stereoselectively based on the Zn(BH4)2 reduction and total synthesis of (+)-pederin (3) was accomplished from 1 and the previously synthesized 2. 相似文献
3.
We describe a short, enantioselective synthesis of the naturally occurring pyrrolizidine alkaloid (+)-latifoline (1) employing a tandem [3,3] sigmatropic rearrangement/[1,2] allyl shift as a key step in constructing (+)-latifolic acid (4). 相似文献
4.
(+)-Thalictrifoline () has been synthesized from an optically resolved (+)-8-oxo-13-carboxytetrahydroprotoberberine () whose absolute configuration was established by correlation with (+)-. This determines the absolute configurations of (+)-thalictrifoline () as 13R, 14R aria (+)-corydalic acid methyl ester () as 3R, 4R. 相似文献
5.
Moldvai I Temesvári-Major E Incze M Szentirmay E Gács-Baitz E Szántay C 《The Journal of organic chemistry》2004,69(18):5993-6000
The first direct synthesis of (+)-lysergic acid (2a) suitable for scale-up has been achieved by the following reaction sequence. Bromoketones 4d or 4g were allowed to react with amine 5 followed by deprotection, and the resulting diketone 6c was transformed into the unsaturated ketone (+/-)-7 by the LiBr/Et(3)N system. Resolution afforded (+)-7, which was further transformed by Sch?llkopf's method into the mixture of esters 2e and 2f. Upon hydrolysis the latter mixture afforded (+)-2a. The peptide part of alpha-ergocryptine (1) was prepared according to the Sandoz method; the stereoefficiency, however, has been significantly improved by applying a new resolution method and recycling the undesired enantiomer. Coupling the peptide part with lysergic acid afforded 1. Having synthetic (+)-7 in hand, we can claim the total synthesis of all the alkaloids which were prepared earlier from (+)-7 that had been obtained through degradation of natural lysergic acid. 相似文献
6.
Asymmetric synthesis of (+)-phosphinothricin, (+)-2-amino-4-phosphono-butyric acid, and their enantiomers has been achieved by the Michael addition of chiral glycine Schiff bases to vinyl phosphorus compounds. 相似文献
7.
Kenji Morokuma 《Tetrahedron letters》2008,49(42):6043-6045
Aldol reaction of di-tert-butyl 4-(4-methoxybenzyloxy)-2-oxobutanoate with pent-4-enal using (S)-1-(3,5-bis(trifluoromethyl)phenyl)-3-(pyrrolidin-2-ylmethyl)thiourea hydrochloride as a catalyst, followed by Pinnick oxidation and tert-butyl esterification, gave (2S,3S)-di-tert-butyl 2-(2-(4-methoxybenzyloxy)ethyl)-3-allyl-2-hydroxysuccinate in high optical purity (85% ee), from which the total synthesis of (+)-trachyspic acid, a tumor cell heparanase inhibitor, was accomplished. 相似文献
8.
(+)-Puraquinonic acid (1a) was synthesized, using a route based on ring-closing metathesis and radical cyclization, the chirality of the quaternary carbon being controlled by a temporary adjacent asymmetric center. 相似文献
9.
Reported herein is a novel approach to the total syntheses of (-)-alpha-kainic acid and (+)-alpha-allokainic acid, where the stereochemistries on C(2), C(3), and C(4) of the pyrrolidine core were introduced efficiently and selectively. A regio- and stereoselective C-H insertion reaction was utilized to prepare the gamma-lactam as an intermediate. A Michael-type cyclization of phenylsulfone with a conjugated acetylenic ketone was developed to prepare the tricyclic ketone as a key intermediate for (-)-alpha-kainic acid. Subsequently, a stereoselective dephenylsulfonylation was carried out successfully to secure the cis relationship at C(3) and C(4) centers. An unprecedented acetylation on the phenylsulfone, followed by a stereoselective dephenylsulfonylation, secured the trans relationship at C(3) and C(4) centers in (+)-alpha-allokainic acid. 相似文献
10.
(+)-Carpamic acid [(2′R,5′S,6′S)-8-(5′-hydroxy-6′-methylpiperidin-2′-yl)octanoic acid, 1] was synthesized from (S)-alanine, employing intramolecular and reductive amination of acyclic amino ketone 8 as the key step to generate the piperidine ring. 相似文献
11.
A new and more efficient route for the conversion of the readily available (+)-Δ3-carene into (+)-trans-chrysanthemic acid is described. 相似文献
12.
Siegfried Huneck John A. Akinniyi A.Forbes Cameron Joseph D. Connolly Alan G. Mulholland 《Tetrahedron letters》1981,22(4):351-352
The absolute configuration of (+)-usnic acid has been shown to be (4aR) as in (1) by X-ray analysis of the (?)-α-phenylethylamine derivative (2). The structure and absolute stereochemistry of (?)-pseudoplacodiolic acid (4) have been established. 相似文献
13.
Daisuke MatsumuraToshimasa Takarabe Takumi TodaTakashi Hayamizu Kiyoto SawamuraKen-ichi Takao Kin-ichi Tadano 《Tetrahedron》2011,67(35):6730-6745
The total syntheses of both natural (+)-spiculoic acid A and (+)-zyggomphic acid, new cytotoxic marine natural products of polyketide origin, have been accomplished for the first time. These syntheses were achieved by the highly stereoselective and high-yielding intramolecular Diels-Alder reaction of a functionalized (E,E,E)-2,7,9-dodecanal derivative to construct the core tetrahydroindan-2-one skeleton. A stereocongener of (+)-spiculoic acid A, i.e., the (2R,5S,6R)-isomer, was also synthesized. The details of these total syntheses are described. 相似文献
14.
It has been found that an ordinary reaction calorimeter can be used for the determination of small heat effects (10^-^3 to 10^-^4 C temperature change) by correctly evaluating the Newton's cooling constant K through a reference temperature technique. This technique was applied to the determination of the integral enthalpies of solution of L(+)-aspartic acid and L(+)-glutamic acid in water in the concentration range of 10^-^3 to 10^-^4 mol/kg which were found equal to 25.8+/-0.6 and 25.7+/-0.4kJ/mol respectively (twice standard deviation). No CH2 increment effect has been revealed in the solution enthalpies of these two amino-acids. 相似文献
15.
The combined use of the Sharpless asymmetric epoxidation, a number of stereospecific chemical transformations, and the 3,5-hexadienoic acid benzannulation protocol allowed us to devise a new, divergent, and stereoselective approach to terpenes with a chiral tertiary hydroxyl group at the ortho-position of a phenol functional group. Accordingly, the natural occurring enantiomeric forms of the bisabolane sesquiterpenes (+)-curcutetraol, (+)-sydonol, (+)-sydonic acid, and (+)-7-O-methylsydonic acid were synthesized with high enantiomeric purity starting from geraniol. The latter two acids were prepared in enantioenriched form for the first time. 相似文献
16.
E-(R)-5-Hydroxy-2-hexenoic acid (4) and the acetonide of E-(4R,5R,7R)-trihydroxy-2-octenoic acid (3) are joined to give, after deprotection, (+)-colletodiol (1). The syntheses of the two hydroxy-acids from poly-(R)-3-hydroxy-butanoate (PHB) and (?)-tartaric acid, respectively, are outlined. 相似文献
17.
A stereocontrolled total synthesis of (+)-lysergic acid (1) is achieved using three metal-catalyzed methodologies for the construction of three key rings. Highlights of the synthesis include Pd-catalyzed indole synthesis to form the B ring, a RCM reaction to form the D ring, and an intramolecular Heck reaction to form the C ring. 相似文献
18.
Stefan Randl 《Tetrahedron letters》2004,45(6):1167-1169
We report herein an efficient enantioselective synthesis of (+)-carpamic acid, with nine steps as the longest linear sequence, the key strategy being based on a novel sequence of a cross-metathesis (CM) reaction and a subsequent cyclizing reductive amination to form the piperidine ring. 相似文献
19.
Summary An EPC (enantiomerically pure compound) synthesis of the antibiotic natural product (+)-heptelidic acid (1) is presented. Key step of the synthesis is a conjugate addition of the acetal protected vinyl cuprate4 to the auxiliary shielded enoate5n which gives the adduct7n as a single diastereomer. After cleavage of the acetal protecting group and of the chiral auxiliary the enantiomerically pure -ketoester12 has been obtained which has been transformed to the title compound1 (11 steps starting from5n, 10.6% overall yield).
EPC-Synthese von (+)-heptelidsäure
Zusammenfassung Eine EPC-Synthese (EPC = enantiomerically pure compound) des antibiotischen Naturstoffes (+)-Heptelidsäure (1) wird präsentiert. Schlüsselschritt der Synthese ist dieMichael-Addition des acetal-geschützten Vinylcuprates4 an das auxiliargeschützte Enoat5n, wobei das Addukt7n in diastereomerenreiner Form erhalten wird. Nach der Abspaltung der Acetalschutzgruppe und des chiralen Auxiliars läßt sich der enantiomerenreine -Ketoester12 herstellen, der in die Titelverbindung1 umgewandelt werden kann (11 Stufen ausgehend von5n, 10.6% Gesamtausbeute).相似文献
20.
Synthesis of (+)-Abscisic Acid . Starting from (4S)-4-hydroxy-2,6,6-trimethylcyclohex-2-enone ( 2 ), a short synthesis of the natural (+)-abscisic acid ((+)- 1 ) has been accomplished. 相似文献