[3,3]-Claisen rearrangements in 24α-methyl steroid synthesis

Хрипач, В. А.; Жабинский, В. Н.; Konstantinova, Olga V.; Khripach, N. B.; Antonchick, Andrey P.; Schneider, Bernd

doi:10.1016/s0039-128x(02)00007-7

Cited by 27 publications

(13 citation statements)

References 19 publications

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“…The Johnson orthoester procedure and the Ireland variant of Claisen rearrangement are frequently employed for the synthesis of stereo-defined C-24 mono-alkylated sterol side-chains. [9][10][11] We also utilized the orthoester Claisen rearrangement for the stereoselective synthesis of (24R)-and (24S)-(22E)-24-isopropenyl-22-dehydrocholesterol and 24-isopropenylcholesterol, another multiply alkylated sterol of T. ophiraphidites. 12 The synthetic route to 1a and 1b, and 2a and 2b is shown in Figure 2.…”

Section: Resultsmentioning

confidence: 99%

C-24 stereochemistry of marine Sterols: (22E)-24-Ethyl-24-methylcholesta-5,22-dien-3b-oβl and 24-Ethyl-24-methylcholest-5-en-3β-ol

Echigo

Castellanos

Duque

et al. 2011

J. Braz. Chem. Soc.

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As configurações dos carbonos C-24 nos compostos (22E)-24-etil-24-metilcolesta-5,22-dien-3b-ol (1) e 24-etil-24-metilcolest-5-en-3b-ol (2), isolados da esponja do caribe colombiano Topsentia ophiraphidites foram determinadas como R e S, respectivamente, com base na comparação dos seus dados de RMN com aqueles de amostras de configurações já definidas 24R e 24S, as quais foram sintetizadas em rotas envolvendo ortoésteres provenientes do rearranjo de Claisen de álcoois D 23-22 alílicos. Este é primeiro estudo de síntese, em que o rearranjo de Claisen é utilizado para introduzir um centro quaternário em C-24, de maneira estereoespecífica e com rendimento aceitável. Análises por difração de raio X de 1 confirmaram essas atribuições estereoquímicas.The C-24 configurations of (22E)-24-ethyl-24-methylcholesta-5,22-dien-3b-ol (1) and 24-ethyl-24-methylcholest-5-en-3b-ol (2), isolated from the Colombian Caribbean sponge Topsentia ophiraphidites, were determined to be R and S, respectively, by comparing their NMR data with those of stereodefined (24R)-and (24S)-samples that were synthesized in routes involving the orthoester Claisen rearrangement of D 23 -22-allylic alcohols. This is the first synthetic study where the Claisen rearrangement is used to introduce a C-24 quaternary center in a stereospecific manner with acceptable yield. X-ray analysis of 1 confirmed these stereochemical assignments.

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Section: Resultsmentioning

confidence: 99%

C-24 stereochemistry of marine Sterols: (22E)-24-Ethyl-24-methylcholesta-5,22-dien-3b-oβl and 24-Ethyl-24-methylcholest-5-en-3β-ol

Echigo

Castellanos

Duque

et al. 2011

J. Braz. Chem. Soc.

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“…Both strategies were used for stereoselective construction of a new carbon skeleton characteristic of brassinolide biosynthetic precursors. Preparation of trideuterated fragment 1 of brassinosteroids was based on our preliminary experience10,11 with Claisen rearrangement for stereoselective construction of the steroidal side chains (Fig. 2).…”

Section: General Considerations and Starting Materialsmentioning

confidence: 99%

“…6). 11 Successive reduction of the ester 33 with LiAlD 4 followed by tosylation and another deuteride reduction of intermediate 26‐tosylate gave compound 34 containing three deuterium atoms in the terminal part of the side chain 25. A further route to the desired deuterated brassinolide biosynthetic precursors involved construction of the steroidal cyclic part.…”

Section: Synthesis Of [26‐2h3]brassinosteroidsmentioning

confidence: 99%

Labeled brassinosteroids for biochemical studies

Хрипач

Жабинский

2007

The Chemical Record

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The present paper describes the results of our studies on the synthesis of brassinolide biosynthetic precursors as tools for investigations of new biosynthetic routes leading to brassinosteroids. The corresponding labeled compounds containing three or six deuterium atoms at terminal methyl group(s) of the side chain (in a position ensuring lack of isotopic exchange) were prepared starting from stigmasterol or bisnorcholenic acid. Two strategies for the construction of the carbon skeleton of the side chain were applied in this study: Claisen rearrangement of allylic alcohols and convergent synthesis based on the coupling of 22-aldehydes with appropriate chiral sulfone. More than 20 brassinolide precursors (actual or suspected) have been prepared for metabolic studies that enabled identification of new brassinosteroids and biosynthetic subpathways to brassinolide in Secale cereale and Arabidopsis thaliana.

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“…Hydrogenation of the oxo-groups of steroids can be achieved both by chemical reductants [6][7][8][9][10] and catalytic hydrogenation [4,5,11], whereas saturation of steroid alkenes is mainly performed by homogeneous and heterogeneous catalytic procedures [4,5,[12][13][14][15]. _______________________ Dedicated to Professor András Lipták on the occasion of his 70 th birthday *Corresponding author.…”

Section: Introductionmentioning

confidence: 99%