Wyniki wyszukiwania - BazTech

1

Asymetryczna aminokataliza : użyteczne narzędzie w tworzeniu chemicznej różnorodności

Skrzyńska Anna, Przydacz Artur, Dyguda Mateusz, Topolska Aleksandra, Albrecht Łukasz

Wiadomości Chemiczne

|

2020

|

[Z] 74, 3-4

255--284

EN

Over the last 20 years asymmetric aminocatalysis has emerged as highly useful and reliable method of asymmetric synthesis. It involves the use of primary or secondary amines as catalysts of various stereoselective transformations of carbonyl substrates. Owing to the diverse activation strategies available in asymmetric aminocatalysis, it became a method of choice when the functionalization of prochiral aldehydes and ketones is considered. As a consequence, a direct and straightforward access to various chiral building blocks is possible that is of relevance to modern stereocontrolled organic synthesis. In the manuscript, the development of various aminocatalytic activation concepts is described and recent, selected contributions to this field of chemistry discussed. Main advantages of these strategies are highlighted providing an overview of this fascinating area of research.

2

Prolina : pospolity aminokwas wyjątkowy katalizator. Część IV, Reakcja Michaela

Karczmarska-Wódzka A., Studzińska R., Kołodziejska R., Wróblewski M., Dramiński M.

Wiadomości Chemiczne

|

2014

|

[Z] 68, 1-2

49--65

EN

In recent years there has been a dynamic development of asymmetric synthesis. Groups of researchers, particularly the one led by Benjamin List and Carlos Barbas, carried out a number of reactions and showed the effectiveness of the use of small organic molecules such as proline as catalysts. Michael addition catalyzed with proline is a particularly interesting reaction because it can be carried out in two aminocatalytic pathways. The analysis of Michael reaction reveals potential for both forms of aminocatalysis: enamine and iminium catalysis (Scheme 1) [1–14]. Presumably Michael reaction proceeds mainly according to enamine mechanism. The use of proline in Michael reaction with imine activated acceptor is slightly effective. So far the researches have shown that the modification of proline molecule or addition of other catalyst is necessary for condensation to appear. Enamine catalysis concerns the activation of carbonyl compound in situ being a donor. There is no need for enolase anion to be created earlier [2, 15–17]. When, as a result of the reaction of a,b-unsaturated carbonyl compound with proline, Michael acceptor activation appears it means that it is enamine mechanism reaction (Scheme 1) [2, 24]. One of the first examples of direct Michael reaction proceeding through enamine transition state is the reaction of cyclopentanone with nitrostyrene (Scheme 6) [20–23]. Other examples of Michael addition of ketone with nitro olefin catalysed by proline are shown in table 2 and 3 [10, 23, 30]. Nitroketones obtained in that way are useful as precursors for different organic compounds [33], also pyrrolidines [34]. Pyrrolidines are pharmacologically active and they selectively block presynaptic dopamine receptors [34] (Scheme 7). Except for Michael intermolecular reaction, intramolecular condensation adducts were also obtained. Michael intramolecular proline-catalyzed condensation in which inactive ketones transform into α,β-unsaturated carbonyl compounds was described (Scheme 9) [35, 36]. These reactions require a stoichiometric amount of a catalyst and a long time of reaction and they give as a result a little enantiomeric excess [11, 24, 35]. In 1991, Yamaguchi and co-workers carried out malonates Michael addition to α, β-unsaturated aldehydes catalyzed by L-proline [24, 39]. The reaction proceeded according to enamine mechanism, for example dimethyl malonate was reacted with hex- 2-enal in the presence of proline to give Michael adduct in 44% yield. To improve the yield an attempt of a slight modification of a proline molecule was made transforming it into proper salt. Proline lithium salt enabled to obtain the condensation product in 93% yield (Tab. 4). Regardless of a used catalyst the products in the form of racemates were obtained. In order to improve enantioselective properties of a catalyst, Michael addition of diisopropyl malonate to cycloheptenone was carried out in chloroform in the presence of different proline salts. Optimal enantioselectivity and yield was obtained by using rubidium salt (Tab. 5–7) [40, 41]. Rubidium prolinate-catalyzed Michael additions are used in industry e.g. for enantioselective synthesis of the selective serotonine reuptake inhibitior (SSRI) (–)-paroxetine (antidepressant) (Scheme 12) [24].

3

Prolina : pospolity aminokwas wyjątkowy katalizator. Część III, Reakcja Mannicha

Studzińska R., Karczmarska-Wódzka A., Wróblewski M., Kołodziejska R., Dramiński M.

Wiadomości Chemiczne

|

2014

|

[Z] 68, 1-2

21--48

EN

Mannich reaction occuring among ketone, aldehyde, and amine is one of the ways of a synthesis of biologically active compounds. Reactions of this type were carried out in the presence of different catalysts [3–10], however in recent years a lot of attention has been paid to enantioselective Mannich reaction catalyzed with proline. Such reactions were carried out with the use of different compounds containing carbonyl group and the most frequently used amine was p-anisidine. The advantage of the use of p-anisidine is a possibility of conducting the direct Mannich reaction (Scheme 3). In this way β-amino ketones (Tab. 1, 2, 4) [15, 18–20, 23, 24], α-hydroxy-β-amino ketones (Tab. 3) [15, 22], and β-amino alcohols (Tab. 5, 6) [25, 26] were obtained. A possibility of syntheses of β-amino sugars and α-amino acids with their derivatives (Tab. 7) [28, 29] is worth noticing. In a great number of described reactions, the products were obtained with satisfactory yield and enantiomeric excess. Taking into consideration the difficulty of a removal of p-hydroxyphenyl group which protects amine group in the resulting products, the attempts of using different amine compounds in Mannich reactions catalyzed with proline were undertaken. The use of amines blocked by tert-butoxycarbonyl group (Boc) enabled to obtain the products with high yield and ee values (Tab. 12–15) [35–38]. However in the case of the use of Boc the reaction must be carried out in an indirect way (it is necessary to prepare imine blocked by Boc earlier).

4

Trans-1,2-diaminocykloheksan – niezwykła kariera outsidera

Petryk M., Kwit M.

Wiadomości Chemiczne

|

2013

|

[Z] 67, 5-6

393--442

EN

An enantiopure trans-1,2-diaminocyclohexane is one of the most widely used chiral diamines in modern organic chemistry. This chiral building block, readily available from waste industrial products, emerges as a major figure in the field of asymmetric synthesis. The unique structural and conformational properties of trans-1,2-diaminocyclohexane make it very useful for the development of new synthetic strategies, taking advantage of its geometrical pre-organization. In this short article, we will highlight the utility of enantiomerically pure trans-1,2-diaminocyclohexane derivatives as broad-range chiral reagents and ligands for catalytic cycles. A brief overview of the aspects of applications in the field of molecular recognition will also be given.

5

Alkaloidy kory chinowej : małe cząsteczki, które wiele mogą

Kacprzak K., Czarnecki P.

Wiadomości Chemiczne

|

2013

|

[Z] 67, 5-6

443--493

EN

Cinchona alkaloids comprising quinine, quinidine, cinchonidine and cinchonine as the major members constitute a unique class of quinoline alkaloids with tremendous impact on human civilization (Section 1). The odyssey of Cinchona alkaloids began with the discovery of their antimalarial properties followed by antiarrhytmic action of quinidine. Currently medicinal chemistry of Cinchona alkaloids derivatives develops rapidly and many other activities such as cytotoxic, multidrug resistance inhibitory have been demonstrated (Section 5) [5]. Beside medicine Cinchona alkaloids gave also the fundaments of stereochemistry and asymmetric synthesis. An extraordinary catalytic potency of parent and modified Cinchona alkaloids (deserving privileged catalyst classification) include more than 50 types of diverse stereoselective reactions, with few spectacular such as asymmetric dihydroxylation of alkenes or heterogeneous α-ketoesters hydrogenation (Section 3) [3]. Last but not least the portfolio of applications of Cinchona alkaloids includes resolution of racemates by diastereomeric crystallization or by the use of Cinchona- -based chiral stationary phases for ion-exchange enantioselective chromatography and other recognition or sensing systems (Section 4) [166]. Easy transformation of Cinchona alkaloids (for example by click chemistry) into other chiral and modular building blocks together with current pressure on a more intense exploration of sustainable products make cinchona alkaloids of primary importance for modern synthetic, catalytic and medicinal chemistry. The aim of this review which covers over 200 references is to briefly summarize all aspects of Cinchona alkaloid chemistry and biology with the special emphasis on new applications.

6

Metody syntezy 2,2'-bipirolidyny

Eichstaedt K.

Wiadomości Chemiczne

|

2012

|

[Z] 66, 5-6

461-483

EN

Vicinal diamine derivatives form an interesting and significant class of organic compounds. They play an essential role as chelating agents and also as ligands for asymmetric synthesis. They are used in synthesis of biologically active substances and in supramolecular chemistry [1–11]. There has been published a great number of reviews concerning the application and synthesis of 1,2-diamines with special emphasis on their organic potential [1–11]. Without any doubt, chiral 2,2’- bipyrrolidine derivatives are representative family of these compounds. They have gained particular attention since they are widely used. A remarkably broad spectrum of synthetic exploration has been reported for these agents [4, 12–14]. This paper provides description of methods for the synthesis of chiral 2,2’-bipyrrolidine. There are only seven different approaches to obtain (R,R) or (S,S)-2,2’-bipyrrolidine, five from which take advantage of stereoselective synthesis steps [15–21]. Nevertheless, a method for the synthesis of amine-1, which connects low reagents price with low time-consuming and high yield have not been described yet. Thus, creation of a new strategy for an efficient synthesis of chiral 2,2’-bipyrrolidine is still a challenging topic of studies.

7

Kwasy nukleinowe jako katalizatory reakcji chemicznych

Bukowiecka-Matusiak M., Sobczak M.

Wiadomości Chemiczne

|

2012

|

[Z] 66, 1-2

119-137

EN

Nucleic acids, due to their specific structure, are effective and durable carriers of genetic information. They have also been used as catalysts in chemical reactions. The right-handed DNA double helix structure has become one of the icons of modern science, and its share in asymmetric catalysis is undeniable. In these reactions, DNA is a source of chirality and proximity between oligonucleotides and complexes of copper during catalysis, what allows a direct transfer of chirality from DNA to the reaction product. Almost complete regioselectivity and excellent enantioselectivity of the aforementioned reactions in water are the evidence of the potential of asymmetry based on DNA. Asymmetric catalysis used in organic synthesis, allows achieving high enantioselectivity. This strategy has been successfully used to create new C-C bonds in Diels- Alder cycloaddition, Friedel-Crafts alkylation and Michael addition using copper complexes with oligonucleotides as catalysts. The important factor to optimize the reaction of asymmetric catalysis in the presence of DNA constitutes its sequence. It has been shown that the use of the double helix DNA can provide the product with higher enantiomeric excess than using the single strand of DNA. In addition, the results of the study suggest that Friedel-Crafts alkylation is accelerated by DNA almost 30-fold. The same correlation is observed in Diels-Alder cycloaddition. Due to promising results, further testing directed at the possibility of using catalytic DNA is being conducted.

8

Ionic liquids as the catalysts for asymmetric reactions

Dąbrowski Z., Wiśniewska A., Kulig-Adamiak A., Kamiński J.

Polimery

|

2012

|

T. 57, nr 5

375-381

EN

A new 7 functionalized chiral ionic liquids (CILs) based on pyrrolidine have been synthesized from (S)-proline as a main substrat. The obtained compounds have 1-[(S)-(pyrrolidin-2-yl)methyl]-3-alkylimidazolium cation and bis(trifluoromethylsulfonyl)imide and hexafluorophosphate anions. The structures of the obtained catalysts were determined by spectroscopic analysis 1H NMR, 13C NMR and 19F NMR. This chiral ionic liquids have been applied as efficient catalysts for Michael addition of cyclohexanone to nitroalkenes.

PL

Na bazie (S)-proliny zsyntezowano 7 nowych funkcjonalizowanych chiralnych cieczy jonowych zawierających kation 1-[(S)-(pirolidyno-2-ylo)metylo]-3-alkiloimidazoliowy oraz aniony: bis(trifluorometylosulfonylo)imidkowy i heksafluorofosforanowy. Struktury uzyskanych związków określono metodami spektroskopowymi 1H NMR, 13C NMR i 19F NMR. Zsyntezowane ciecze jonowe zastosowano jako skuteczne katalizatory addycji Michaela cykloheksanonu do nitroalkenów.

9

Chiralne katalizatory organiczne w asymetrycznej reakcji Michaela

Albrecht Ł., Krawczyk H.

Wiadomości Chemiczne

|

2009

|

[Z] 63, 5-6

391-436

EN

In marked contrast to enantioselective Michael reactions promoted by chiral Lewis acids, organocatalytic Michael reactions have not been used as standard transformation in organic chemistry until quite recently. During the past few years chiral organocatalysts have emerged as a broadly applicable class of catalysts for enantioselective Michael reaction. This review summarizes these advances emphasizing the structural and mechanistic features that contribute to high enantioselectivity in organocatalytic Michael reactions. The first part of this review deals with the development of covalent catalysis in organocatalytic asymmetric Michael reactions. To date, several chiral secondary amines have been employed to promote formation of electron-rich enamines from enolizable aldehydes and ketones, which then react with various ?,?-unsaturated electrophiles to afford products [7-24]. In contrast, chiral imidazolidinones and diarylprolinol ethers are most often used to activate ?,?-unsaturated carbonyl compounds by forming electron-deficient iminium ions, which render the ?-carbon more electrophilic then their carbonyl precursors for nucleophilic attack [2a, 7, 25-34]. The second part of this review documents the development of non-covalent catalysis [35-64]. In this regard, chiral Bronstedt bases [35-39], chiral phase-transfer catalysts [40-49] and chiral hydrogen-bond donors [50-64] have emerged in the past few years as readily accessible organocatalysts of asymmetric Michael reaction. The most efficient catalysts such as cinchona alkaloids and their derivatives, quaternary ammonium salts obtained from cinchona alkaloids and chiral thiourea derivatives, respectively are revived and the modes of actions are discussed. Furthermore, the major developments of organocatalytic asymmetric Michael reactions are also reviewed.

10

Asymetryczna synteza α, β-diaminokwasów

Błaszczyk R., Gajda T.

Wiadomości Chemiczne

|

2009

|

[Z] 63, 7-8

635-684

EN

Through the years, α,β-diamino ac6ds and their derivatives have attracted a great deal of attention among organic chemists because of their biological significance [1, 2]. This review deals with the synthetic approaches of α,β-diamino acids and their derivatives (e.g., esters, amides) using asymmetric synthesis methods described in the literature up to the end of 2008. Aziridines and 3-amino-β-lactams are beyond the scope of this review and will be only considered as intermediates in the synthesis of acyclic derivatives. The methods found in the literature can be classified essentially in two main categories: methods that require a new carbon-carbon single bond construction and method based on the functional groups transformation reactions within the carboxylic acids skeleton. A great number of C-C forming methods are the addition reactions of glycine derivatives or nitro compounds to imines (Mannich-type reactions). The asymmetric induction requires chiral substrate usage (e.g., chiral sulfinimines, chiral glycinates) [30-37, 61-67] or results from the application of chiral catalysts (e.g., chiral Lewis acids, chiral PTC catalysts and other organocatalysts) [39-48, 50-60] . Strecker's reaction using chiral imines or related compounds is also often used [69-77]. Methods begining from the existing carbon skeleton and based on the modification of the functional groups are as follows: catalytic asymmetric diamination and aminohydroxylation of α,β-unsaturated carboxylic esters [92-100, 107-109]. Subsequent transformation of the hydroxy group into the amine group in the hydroxyamino acids derivatives is then necessary [100-109]. The direct introduction of the amino moiety into the β-amino esters via electrofilic amination is also described [120-131]. The title compounds can also be obtained by catalytic enantioselective reduction of dehydrodiamino acids derivatives[117-119].

11

Badania nad syntezą chlorowodorku (2R,3S)-3-fenyloizoseryny

Jezierska-Zięba M., Kąkol B., Obukowicz B., Cybulski J., Fedoryński M., Szpakiewicz M.

Przemysł Chemiczny

|

2007

|

T. 86, nr 4

318-323

12

Synthesis of the Enantiomers of 1-{2-Hydroxy-3-[4-(2-hydroxy-phenyl)-piperazin-1-yl]-propyl}-pyrrolidin-2-one Using Soluble and Polystyrene Bound SalenCo(III)OAc Complexes as Catalysts of Hydrolytic Kinetic Resolution

Kulig K., Nowicki P., Malawska B.

Polish Journal of Chemistry

|

2007

|

Vol. 81, nr 2

179-186

EN

The asymmetric synthesis of 1-{2-hydroxy-3-[4-(2-hydroxy-phenyl)-piperazin-1-yl]- propyl}-pyrrolidin-2-one 3 is described. Enantiomers of compound 3 were synthesized by hydrolytic kinetic resolution (HKR) of racemic 1-oxiranylmethyl-pyrrolidin-2-one rac-2 using soluble or polystyrene bound salenCo(III)OAc complexes folowing its aminolysis with 1-(2-hydroxy-phenyl)-piperazine. The enantiomeric purity of obtained dihydrochloride salts of compounds 3was determined by HPLC method with Chiralpack IA column. The ees determined for enantiomers of compound 3 were in range 92–96% and indicated that proposed methods are effective tools for the synthesis of aminoalcohols. The application of polystyrene bound catalyst of HKR enables its easy isolation from reaction mixture and recovery.

13

Synthesis and Selected Transformations of Optically Active Cyclopentenyl Sulfoxides: New Approach o Optically Active Cyclopentenones

Midura W., Krysiak J., Wieczorek M., Filipczak A.

Polish Journal of Chemistry

|

2007

|

Vol. 81, nr 2

211-223

EN

The tandem Michael addition – Horner olefination reaction of (S)- alfa-(diethoxyphosphoryl) vinyl p-tolyl sulfoxide was applied for the synthesis of optically active cyclopentenyl sulfoxides, whichwere converted into the corresponding cyclopentenones by Pummerer reaction with trifluroacetic anhydride. The sequence comprising the tandem Michael – Horner reaction, separation of diastereomers and Pummerer reaction afforded enantiomerically pure substituted cyclopentenones.

14

Narzędzia chemii kombinatorycznej. Cz. 4. Synteza asymetryczna na fazie stałej

Łaźny R., Nodzewska A., Żabicka B.

Wiadomości Chemiczne

|

2006

|

[Z] 60, 3-4

191-255

EN

Solid Phase Asymmetric Synthesis (SPOS) is a recently introduced term embracing all methods of asymmetric synthesis involving use of solid supported substrates and reagents. This review presents basic definitions of asymmetric synthesis and currently used concepts for enatioselective and diastereoselective transformations involving supported synthesis. The concepts of chiral auxiliary, chiral catalyst and chiral reagent are illustrated with selected but fairly comprehensive overview of methods published till January 2005. In particular use of chiral auxiliaries such as oxazolidine derivatives, amines, hydrazines, sulfoxides, sulfinyl amides, sulfoxy imines, carbohydrates and alcohols is covered. Applications of immobilized chiral catalysts to synthesis of carbon-carbon bonds, carbon-hydrogen bonds, carbon--heteroatom bonds and in phase-transfer catalysis is presented with selected reactions due to huge volume of literature in this field. Moreover applications of chiral catalysts and chiral reagents in reactions of immobilized substrates and use of chiral immobilized reagents is also reviewed. The literature review shows that the most popular methods of supported asymmetric synthesis are the alkylation of enolates, aldol reactions, Grignard reactions, cycloadditions, reduetion of ketones, epoxida-tions, olefin dihydroxylation, and phase-transfer catalyzed reactions. There are numerous applications of immobilized chiral catalysts and a substantial number of applications of immobilized chiral auxiliaries. On the other hand there are only scarce reports of applications of chiral reagents and chiral catalysts to the reactions of achiral immobilized substrates.

15

Diastereoselective Addition of Grignard Reagents to Chiral alfa-Ketoimides Derived from Oppolzer's Sultam

Raszplewicz K., Sikorska L., Kiegiel K., Bałakier T., Jurczak J.

Polish Journal of Chemistry

|

2005

|

Vol. 79 / nr 12

1901-1907

EN

Additions of various Grignard reagents to N-pyruvoyl- (3) and N-phenylglyoxyloyl- (2R)-bornane-10,2-sultam (4) under thermal and Lewis-acid catalytic conditions are studied. High diastereoselectivity was observed in these reactions, and in the case of vinylmagnesium bromide additions to -ketoimide 4 a change of direction of asymmetric induction was found.

16

Asymmetric Synthesis of Multi-substituted Indolizidines by Intramolecular Addition of Allylsilane to Chiral 2,3-Dihydro-4-pyridones

Furman B., Frelek J., Dziedzic M., Kamińska A.

Polish Journal of Chemistry

|

2005

|

Vol. 79 / nr 12

1919-1928

EN

A short and synthetically attractive asymmetric synthesis of substituted indolizidines is described. The discovered reaction sequence consists of the asymmetric aza-Diels-Alder reaction of aldimines with Danishefsky's diene and the intramolecular Hosomi-Sakurai allylation. The absolute configuration of cycloadducts was established by CD-spectroscopy

17

Asymetryczna synteza a-aminokwasów

Dąbrowska A., Wiczk W., Łankiewicz L.

Wiadomości Chemiczne

|

1998

|

[Z] 52, 1-2

1-42

EN

a-Amino acids are among the most important compounds in living organisms. Amino acids are not only constituents of peptides and proteins but they play an important role in many reactions in living cells. There are many excellent methods of the asymmetric synthesis of a-amino acids, but only some of them are versatile. In this work we have reviewed and presented the most versatile methods, giving the best chemical yield and optical purity of the final products. One of the oldest and still useful synthetic routes to racemic a-amino acids is Strecker's method [3], (Scheme 1). Modification of the methods by Weinges et al. [8-11] (Scheme 2) allowed to obtain pure enantiomers of a-amino acids in high yields. Next important group of the methods applies 'glycine anion equivalent'. In this group, 'bislactim-ether' method of Schöllkopf et al. [13-21], (Scheme 3 and Tab. 1] has to be mentioned at first because of the high chemical yield of the transformation and optical purity of the final amino acid. The same type of methodology was employed by Seebach et al., their method utilizing oxazolidinones or imidazolidinones [22-26] (Schemes 4, 5 and Tab.2). Yield and enantiomeric excess (ee) of the final amino acid in the method of Seebach et al., is very high (in most cases >80%). The only inconvenience is connected with drastic conditions of final hydrolysis. The similar, good results were also obtained in methods utilizing enolates obtained from oxazinones [29-31], (Schemes 6-8 and Tabs 3,4). Derivatives of the oxazinones were also applied as 'glycine cation equivalent' in the method in which 'the chiral cation' reacts with nucleophiles [32, 33], (Scheme 9 and Tab.5) with the high chemical yield and ee of the final product. The similar procedures were used in an alkylation of a chiral Schiff base. The best yields and optical purity of the final a-amino acid were obtained by Oppolzer et al. [35,36], who applied a derivative of glycine attached to bornane-10,2-sultam (the derivative of camphor), (Schemes 13,14). The next group of synthetic procedures is based on a reaction of a ring opening of b-lactones obtained from serine [41-43], (Scheme 16) or threonine [44], and aziridines [45-48], (Scheme 17). A nucleophile attack on the b-carbon of the substrate gives amino acid with modified side chain. Despite the high yield and ee selection of possible nucleophiles is limited. Another important methodology is called 'electrophilic amination'. In this procedure a chiral enolate obtained from N-acyl-oxazolidinone [50,52], (Scheme 18,19) or N-acyl-sultam [51, 53 ], (Scheme 21) is aminated either by di-tert-butyl-azodicarboxylate (DBAD), [50, 51], trisyl azide [52], or 1-chloro-1-nitrozo-cyclohexane [53]. Yield of these reactions are high and ee exceeds 95%. Contrary to the 'electrophilic', a 'nucleophilic amination' requires a 'cation equivalent' obtained from a chiral N-acyl-derivatives [54-55]. The reaction usually yields a desired product of good enantiomeric quality. In most cases azide anion is a source of 'nucleophilic amine equivalent' (Schemes 22 and 23). The chiral 2,3-epoxy-1-ols can be also applied in this methodology [57, 58], (Scheme 24). Asymmetric catalytic hydrogenation of a dehydro derivatives of amino acids and peptides is another valuable group of synthetic routes to the single enantiomer of the amino acid. There is a possiblity of heterogenous and homogenous catalysis involving insoluble catalysis [60, 61], (Schemes 25, 26) or soluble [62, 63], (Schemes 27, 28) in medium of the reaction. The best results (yield = 100% and ee>99%) were reprted for the complexes of Rh with chiral phosphines ligands like BINAP or DIPAMP (Scheme 28), [67]. The last method reported in our review is based on the usage of enzymes. The most widely used in this field are the following enzymes : acylases - catalyzing stereoselective removal or synthesis of N-acyl deerivatives [70], (Scheme 30) and proteases - catalyzing methods give in many cases both enantiomers at the same time.

18

Total synthesis of (+)- and (-)-corydalisol

Chrzanowska M., Józkowiak J., Rozwadowska M.D., Sulima A.

Polish Journal of Chemistry

|

1998

|

Vol. 72, nr 11

2399-2404

EN

The first total synthesis of enantiomerically enriched (+)- and (-)-corydalisol (1) has been performed by addition of lithiated optically pure 1,3-dithiane 3b to hydrastinine chloride (2a), followed by desulfurization, separation of diastereomers and reduction with lithium aluminum hydride.