Enantioselektive Synthese von <scp>D</scp>‐<i>threo</i>‐β‐Hydroxy‐α‐aminosäuren mit Titan‐Kohlenhydrat‐Komplexen

Bold, Guido; Duthaler, Rudolf O.; Riediker, Martin

doi:10.1002/ange.19891010427

Cited by 42 publications

(5 citation statements)

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“…These α‐isothiocyanate methodologies afford thiocarbamate heterocycles as products, which conveniently serve to protect the amine and alcohol functionalities of the aldol adducts, but require a three‐step procedure to reveal the embedded α‐amino acids. Methods employing chiral glycine enolate equivalents have also been reported by the groups of Bold,32 Iwanowicz,33 Caddick,34 and Franck 35. Hydroxymethylations of alanine equivalents to form α‐alkyl serine derivatives have also been reported 36…”

Section: Methodsmentioning

confidence: 94%

A Nickel‐Containing Model System of Acireductone Dioxygenases that Utilizes a C(1)‐H Acireductone Substrate

Allpress

Berreau

2014

Eur J Inorg Chem

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β‐Hydroxy‐α‐amino acids figure prominently as chiral building blocks in chemical synthesis and serve as precursors to numerous important medicines. Reported herein is a method for the synthesis of β‐hydroxy‐α‐amino acid derivatives by aldolization of pseudoephenamine glycinamide, which can be prepared from pseudoephenamine in a one‐flask protocol. Enolization of (R,R)‐ or (S,S)‐pseudoephenamine glycinamide with lithium hexamethyldisilazide in the presence of LiCl followed by addition of an aldehyde or ketone substrate affords aldol addition products that are stereochemically homologous with L‐ or D‐threonine, respectively. These products, which are typically solids, can be obtained in stereoisomerically pure form in yields of 55–98 %, and are readily transformed into β‐hydroxy‐α‐amino acids by mild hydrolysis or into 2‐amino‐1,3‐diols by reduction with sodium borohydride. This new chemistry greatly facilitates the construction of novel antibiotics of several different classes.

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Section: Methodsmentioning

confidence: 94%

A Nickel‐Containing Model System of Acireductone Dioxygenases that Utilizes a C(1)‐H Acireductone Substrate

Allpress

Berreau

2014

Eur J Inorg Chem

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Section: Methodsmentioning

confidence: 94%

Synthesis of Bulk Kesterite – A Prospective Photovoltaic Material

et al. 2014

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A rapid development of photovoltaics has been observed recently. Permanent interest in new cheap and efficient photovoltaic devices stimulates a constant search for new semiconductor materials and structures. The success of materials based on CIGS (CuIn 1-x Ga x Se 2 ) is limited by the prohibitive prices of the elements In and Ga. A family of quaternary semiconducting materials of the Cu 2 ZnSnS 4 type, crystallizing mainly in the kesterite structure, offers a promise of new

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“…The ligand of choice is the diphenyl derivative (R, R)- (17), accessible from natural tartaric acid in 88 % yield. Upon reaction with CpTiC13 it forms a stable chloro chelate (R, R)- (18), which serves as precursor (30), prepared in situ from lithium enolate (29) and the chloro complex (9), reacts with aldehydes to give /3-hydroxy esters (32). [13] This route is particularly interesting for a,@unsaturated aldehydes, since their aldols cannot be obtained from Eketo esters by enantioselective hydrogenation.…”

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confidence: 99%

“…Finally, carbohydrate-modified titanium reagents can be used in the functionalization of amino acids. [18] Transmetalation of the lithium enolate of the N-protected glycine ester (41) generates the DAGO titanium enolate (42), which attacks the re-face of an aldehyde and thus affords the D-syn-Phydroxy-aamino acid ester (43). In a complementary fashion, the threitol complex (44), obtained from the same lithium enolate by transmetalation using (R,R)- (18), adds to the si-face of butyraldehyde and thus leads to the L-amino acid ester ~44.5) (Scheme 4).…”

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Carbohydrate Complexes in Enantioselective Carbon‐Carbon Bond Formation

Dtz¹

1995

Organic Synthesis Highlights II

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The remarkable progress that has been achieved in stereoselective carbon-carbon bond formation is mostly due to the development of novel organometallic reagents. An already classical example is provided by organotitanium compounds, the synthetic potential of which was recognized in the early 1980s.[ 11 In comparison with Grignard and organolithium compounds from which they are generated by a simple in-situ transmetalation, the titanium reagents exhibit an often dramatically improved chemo-and diastereoselectivity, as shown by the addition to aldehydes and ketones.[2] Whereas methyl lithium (la) cannot differentiate between benzaldehyde and acetophenone the methyl titanium reagent (I b) is perfectly aldehyde selective (Scheme 1). Equally impressive is the diustereoselectivity thatin favor of the Cram product (3u) -is observed in the addition of (1 b) to chiral aldehydes such as (2). In contrast, powerful enuntioselective methods have been restricted to a few examples for a long time (e.g. (4) -+ (5) [3]). Obviously, the incorporation of chelating ligands into compounds of type (6u) is not necessarily associated with a sufficient stability of configuration.This goal, however, is achieved if a pentuhupto cyclopentadienyl ligand is incorporated into the reagent. Coordination of chiral coligands (two unidentate coligands X or one bidentate coligand with C2-symmetry to avoid the generation of an undesired metal stereo-center) leads to compounds of type (6b). Carbohydrates turned out to be especially effective in reagents that allow high asymmetric induction both in the nucleophilic addition to aldehydes and in aldol reactions.[4] A potent allyl transfer reagent is complex (10) which can be prepared in a 1OOg scale from the chloro precursor (9) following a twostep sequence from cyclopentadienyltitanium trichloride (7) and diacetone glucose (DAGOH) (8).[5] Complex 10 prefers addition to the re--face of aldehydes, thereby affording homoallyl alcohols (11) in good chemical yields (50-90%) and very good enantioselectivity (86-95 % ee). The selectivity depends only to a minor extent on the temperature, as shown in the addition of (10) to benzaldehyde: The ee value drops from 90 % to 80% when the temperature is raised from -74°C to 0°C. Controlled hydrolysis of the reaction mixture affords undefined titanate species that are transformed to the trichloride (7). Thus, both the metal component and the released chiral auxiliary can be recovered (Scheme 2).The enantioselectivity of the allyl transfer depends markedly on the combination of the coligands: It is essential that two carbohydrate ligands are attached to the metal center together with one allyl group. The ee value of the allylation of benzaldehyde decreases to 46 % and 21 %, respectively, if the bis(diacetone glucose) complex CpTiC1(ODAG)2 (20) Organic Synthesis Highlights I1Edited by Herbert Waldmann OVCH Verlagsgesellschafi mbH,1995

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Enantioselektive Synthese von D‐threo‐β‐Hydroxy‐α‐aminosäuren mit Titan‐Kohlenhydrat‐Komplexen

Abstract: , Rudolf 0. Duthalev und Marfit? RiedikerStimuliert durch die Isolierung von strukturell interessanten, ungewohnlichen a-Aminosluren rnit bemerkenswerten biologischen Eigenschaften I1 wurden bei der enantioselekti-

Cited by 42 publications

References 36 publications

A Nickel‐Containing Model System of Acireductone Dioxygenases that Utilizes a C(1)‐H Acireductone Substrate

A Nickel‐Containing Model System of Acireductone Dioxygenases that Utilizes a C(1)‐H Acireductone Substrate

Synthesis of Bulk Kesterite – A Prospective Photovoltaic Material

Carbohydrate Complexes in Enantioselective Carbon‐Carbon Bond Formation

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