Facile Syntheses of Brassinosteroids: Brassinolide, Castasterone, Teasterone and Typhasterol

Aburatani, Masakazu; Takeuchi, Tadashi; Mori, Kenji

doi:10.1080/00021369.1987.10868284

Cited by 5 publications

(5 citation statements)

References 3 publications

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“…This method has been proposed to obtain terminal double bonds from carboxylic acids [ 32 ], and has been used for the degradation of bile acid side chains [ 33 ], synthesis of BR analogs [ 14 , 15 , 17 ], and specifically for decarboxylation of the side chain of hyodeoxycholic acid ( 4 ) and derivatives [ 34 , 35 ]. Alternatively, the carboxylic degradation reaction may be carried out using PhI(OAc) 2 /CuSO 4 system [ 13 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. Hyodeoxycholic acid ( 4 ) is a common starting material because it is easily available, and it has been previously used to synthesize a number of BR analogs.…”

Section: Resultsmentioning

confidence: 99%

“…In order to obtain 2-deoxybrassinosteroid analogs 18 and 19 a lactone group (B-homo-7-oxa and B-homo-6-oxa) must be introduced in the B ring of 21a ( Scheme 2 ). It is known that Baeyer-Villiger oxidation of 5α-6-keto-steroids with oxygenated substituents at 2α−3α and 3α positions occurs with regioselective control, favoring 7-oxalactone formation, when electron-withdrawing substituents (acetyl [ 13 , 35 , 36 , 37 , 43 , 50 ], benzoyl [ 36 , 50 ], tosyl [ 36 , 50 ], trifluoroacetyl [ 50 ] and acetonide [ 42 ] groups) are present in the C-3 position [ 50 ]. Also, the use of CF 3 CO 3 H as the oxidant agent has a marked effect upon the 6-oxa/7-oxa ratio, and can lead to preferential formation of the desired 7-oxa isomer [ 50 ].…”

Section: Resultsmentioning

confidence: 99%

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Synthesis of 2-Deoxybrassinosteroids Analogs with 24-nor, 22(S)-23-Dihydroxy-Type Side Chains from Hyodeoxycholic Acid

et al. 2018

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Natural brassinosteroids are widespread in the plant kingdom and it is known that they play an important role in regulating plant growth. In this study, two new brassinosteroid analogs with shorter side chains but keeping the diol function were synthesized. Thus, the synthesis of 2-deoxybrassinosteroids analogs of the 3α-hydroxy-24-nor, 22,23-dihydroxy-5α-cholestane side chain type is described. The starting material is a derivative from hyodeoxycholic acid (4), which was obtained with an overall yield of 59% following a previously reported five step route. The side chain of this intermediate was modified by oxidative decarboxylation to get a terminal olefin at the C22-C23 position (compound 20) and subsequent dihydroxylation of the olefin. The resulting epimeric mixture of 21a, 21b was separated and the absolute configuration at the C22 carbon for the main product 21a was elucidated by single crystal X-ray diffraction analysis of the benzoylated derivative 22. Finally, lactonization of 21a through a Baeyer-Villiger oxidation of triacetylated derivative 23, using CF3CO3H/CHCl3 as oxidant system, leads to lactones 24 and 25 in 35% and 14% yields, respectively. Deacetylation of these compounds leads to 2-deoxybrassinosteroids 18 and 19 in 86% and 81% yields. Full structural characterization of all synthesized compounds was achieved using their 1D, 2D NMR, and HRMS data.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Synthesis of 2-Deoxybrassinosteroids Analogs with 24-nor, 22(S)-23-Dihydroxy-Type Side Chains from Hyodeoxycholic Acid

et al. 2018

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“…At first (22E,24S )-3β,5-cyclo-24ethylcholest-22-en-6-one 1 was prepared from stigmasterol as described by Lichtblau. 5 Then the cyclopropane ring was opened with AcOH and H 2 SO 4 to give (22E,24S )-3β-hydroxy-24-ethyl-5α-cholest-22-en-6-one in a similar manner as Aburatani et al 6 had described for the preparation of (22R,23R,24S )-3β,22,23-triacetoxy-5α-ergostan-6-one. In the next steps the hydroxy and the keto groups were protected as acetoxy and ethylenedioxy, respectively.…”

Section: Resultsmentioning

confidence: 98%

Synthesis and crystal structure of [26,27-2H6] 24-epi-cathasterone

Kolbe

Fuchs

Porzel

et al. 2002

J. Chem. Soc., Perkin Trans. 1

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“…Many analogues of brassinolide as plant regulators have been isolated from a wide variety of plants, and many attempts have been undertaken to synthesize these brassinosteroids, see, for example: Aburatani et al (1987); Brosa et al (2001); Brosa & Santamarta (1999); McMorris et al (1993); Clouse (1996Clouse ( , 2002. For related structures, see: Chen et al (2009); Xia et al (2005).…”

Section: Related Literaturementioning

confidence: 99%