Abstract
A number of novel brassinosteroid analogues were synthesized and subjected to the rice leaf lamina inclination bioassay. Modified B-ring analogues included lactam, thiolactone, cyclic ether, ketone, hydroxyl, and exocyclic methylene derivatives of brassinolide. Those derivatives containing polar functional groups retained considerable bioactivity, whereas the exocyclic methylene compounds were devoid of activity. Analogues containing normal alkyl and cycloalkyl substituents at C-24 (in place of the isopropyl group of brassinolide) showed an inverse relationship between activity and chain length or ring size, respectively. The corresponding cyclopropyl and cyclobutyl derivatives were significantly more active than brassinolide and appear to be the most potent brassinosteroids reported to date. When synergized with the auxin indole-3-acetic acid (IAA), their bioactivity can be further enhanced by 1–2 orders of magnitude. The cyclopropyl derivative, when coapplied with the auxin naphthaleneacetic acid, gave a significant increase in yield of wheat in a field trial. Certain 25- and 26-hydroxy derivatives are known metabolites of brassinosteroids. All of the C-25 stereoisomers of 25-hydroxy, 26-hydroxy, and 25,26-dihydroxy derivatives of brassinolide were prepared and shown to be much less active than brassinolide. This indicates that they are likely metabolic deactivation products of the parent phytohormone. A series of methyl ethers of brassinolide was synthesized to block deactivation by glucosylation of the free hydroxyl groups. The most significant finding was that the compound where three of the four hydroxyl groups (at C-3, C-22, and C-23) had been converted to methyl ethers retained substantial bioactivity. This type of modification could, in theory, allow brassinolide or 24-epibrassinolide to resist deactivation and thus offer greater persistence in field applications. A series of nonsteroidal mimetics of brassinolide was designed and synthesized. Two of the mimetics showed significant bioactivity and one had bioactivity comparable to brassinolide, but only when formulated and coapplied with IAA. They thus represent the first nonsteroidal analogues possessing brassinosteroid activity.
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References
G Adam V Marquardt (1986) ArticleTitleBrassinosteroids. Phytochemistry 25 1787–1799 Occurrence Handle10.1016/S0031-9422(00)81151-6 Occurrence Handle1:CAS:528:DyaL28XlsV2ltbk%3D
Adam, G, Porzel, A, Schmidt, J, Schneider, B, Voigt, B (1996) “New developments in brassinosteroid research.” In: Atta-ur-Rahman (Ed.)., Studies in natural products chemistry, Vol. 18., Elsevier, Amsterdam, pp 495–549
G Adam B Schneider (1999) Uptake, transport and metabolism. A Sakurai T Yokota SD Clouse (Eds) Brassinosteroids: steroidal plant hormones. Springer-Verlag Tokyo 113–136
M Anastasia P Allevi MG Brasca P Ciuffreda A Fiecchi (1984) ArticleTitleSynthesis of (2R,3S,22S,23S)-2,3,22,23-tetrahydroxy-B-homo-6-aza-5α-stigmastan-7-one, an aza-analogue of brassinolide. Gazz Chim Ital 114 159–161 Occurrence Handle1:CAS:528:DyaL2cXlvFahur0%3D
M Anastasia P Allevi P Ciuffreda A Fiecchi A Scala (1986) ArticleTitleSynthesis of (2R,3S,22S,23S)-2,3,22,23-tetrahydroxy-B-homo-7-aza-5α-stigmastan-6-one, an aza-analogue of homobrassinolide. J Chem Soc Perkin Trans 1 2117–2121
DL Andersen TG Back L Janzen K Michalak RP Pharis GCY Sung (2001) ArticleTitleDesign, synthesis and bioactivity of the first nonsteroidal mimetics of brassinolide. J Org Chem 66 7129–7141 Occurrence Handle10.1021/jo015832+ Occurrence Handle1:CAS:528:DC%2BD3MXmvVKit7g%3D Occurrence Handle11597241
TG Back (1995) Stereoselective synthesis of brassinosteroids. Atta-ur-Rahman (Ed.), Studies in natural products chemistry, Vol. 16. Elsevier Amsterdam 321–364
Back TG, Baron DL, Luo W, Nakajima SK, Janzen L, Pharis RP. 1997a. A concise synthesis of brassinolide and the preparation and bioactivity of some novel analogues. Proceedings of the 24th Annual Meeting of the Plant Growth Regulation Society of America. Atlanta, p 107–110.
TG Back DL Baron W Luo SK Nakajima (1997b) ArticleTitleConcise improved procedure for the synthesis of brassinolide and some novel side-chain analogues. J Org Chem 62 1179–1182 Occurrence Handle1:CAS:528:DyaK2sXovVynsw%3D%3D
TG Back L Janzen SK Nakajima RP Pharis (1999) ArticleTitleSynthesis and biological activity of 25-methoxy, 25-fluoro and 25-azabrassinolide and 25-fluorocastasterone. Surprising effects of heteroatom substituents at C-25. J Org Chem 64 5494–5498 Occurrence Handle10.1021/jo990312o Occurrence Handle1:CAS:528:DyaK1MXjvFGiu7c%3D Occurrence Handle11674612
TG Back L Janzen SK Nakajima RP Pharis (2000a) ArticleTitleEffect of chain length and ring size of alkyl and cycloalkyl side chain substituents upon the biological activity of brassinosteroids. Preparation of novel analogues with activity exceeding that of brassinolide. J Org Chem 65 3047–3052 Occurrence Handle1:CAS:528:DC%2BD3cXisVKksLY%3D
TG Back SK Nakajima J Zhu (2000b) ArticleTitleSynthesis of 25-hydroxy, 26-hydroxy and 25,26-dihydroxybrassinolide. Synlett . 1649–1651
Back TG, Pharis RP, Nakajima SK. 2001. Brassinosteroid Analogs Useful as Plant Growth Regulators, U.S. Patent 6,239,073, issued May 29, 2001.
TG Back L Janzen RP Pharis Z Yan (2002) ArticleTitleSynthesis and bioactivity of C-2 and C-3 methyl ether derivatives of brassinolide. Phytochemistry 59 627–634 Occurrence Handle10.1016/S0031-9422(02)00019-5 Occurrence Handle1:CAS:528:DC%2BD38XhsFagur8%3D Occurrence Handle11867094
DL Baron W Luo L Janzen RP Pharis TG Back (1998) ArticleTitleStructure–activity studies of brassinolide B-ring analogues. Phytochemistry 49 1849–1858 Occurrence Handle10.1016/S0031-9422(98)00367-7 Occurrence Handle1:CAS:528:DyaK1MXhvFGisg%3D%3D
C Brosa (1996) ArticleTitleBrassinosteroids: a new way to define the structural requirements. Tetrahedron 52 2435–2448 Occurrence Handle10.1016/0040-4020(95)01065-3 Occurrence Handle1:CAS:528:DyaK28XhtVajtbo%3D
C Brosa (1997) Biological effects of brassinosteroids. EJ Parish WD Nes (Eds) Biochemistry and function of sterols CRC Press Boca Raton, FL 201–220
C Brosa L Soca E Terricabras JC Ferrer A Alsina (1998) ArticleTitleNew synthetic brassinosteroids: a 5α-hydroxy-6-ketone analog with strong plant growth promoting activity. Tetrahedron 54 12337–12348 Occurrence Handle10.1016/S0040-4020(98)00743-1 Occurrence Handle1:CAS:528:DyaK1cXmtlSmu7s%3D
C Brosa (1999) Structure–activity relationship. A Sakurai T Yokota SD Clouse (Eds) Brassinosteroids: steroidal plant hormones Springer-Verlag Tokyo 191–222
SD Clouse JM Sasse (1998) ArticleTitleBrassinosteroids: essential regulators of plant growth and development. Annu Rev Plant Physiol Plant Mol Biol 49 427–451 Occurrence Handle1:CAS:528:DyaK1cXjvVShu7o%3D
HG Cutler T Yokota G Adam (Eds) (1991) Brassinosteroids: chemistry, bioactivity and applications. ACS Symp Ser 474. American Chemical Society Washington, DC
S Fujioka A Sakurai (1997) ArticleTitleBrassinosteroids. Natural Prod Rep 14 1–10 Occurrence Handle1:CAS:528:DyaK2sXhvVyjsbY%3D
S Fujioka T Noguchi S Takatsuto S Yoshida (1998) ArticleTitleActivity of brassinosteroids in the dwarf rice lamina inclination bioassay. Phytochemistry 49 1841–1848 Occurrence Handle10.1016/S0031-9422(98)00412-9 Occurrence Handle1:CAS:528:DyaK1MXhvFGjuw%3D%3D
MD Grove GF Spencer WK Rohwedder N Mandava JF Worley JD Warthen Jr GL Steffens JL Flippen–Anderson JC Cook Jr (1979) ArticleTitleBrassinolide, a plant growth-promoting steroid isolated from Brassica napus pollen. Nature 281 216–217 Occurrence Handle1:CAS:528:DyaL3cXht1CrtLY%3D
T Hai B Schneider G Adam (1995) ArticleTitleMetabolic conversion of 24-epi-brassinolide into pentahydroxylated brassinosteroid glucosides in tomato cell cultures. Phytochemistry 40 443–448 Occurrence Handle10.1016/0031-9422(95)00224-U Occurrence Handle1:CAS:528:DyaK2MXot1Gitro%3D
Y Kamuro S Takatsuto (1999) Practical application of brassinosteroids in agricultural fields. A Sakurai T Yokota SD Clouse (Eds) Brassinosteroids: steroidal plant hormones Springer-Verlag Tokyo 223–241
VA Khripach VN Zhabinskii AE de Groot (1999) Brassinosteroids: a new class of plant hormones. Academic Press San Diego, CA
T Kishi K Wada S Marumo K Mori (1986) ArticleTitleSynthesis of brassinolide analogs with a modified ring B and their plant growth-promoting activity. Agric Biol Chem 50 1821–1830 Occurrence Handle1:CAS:528:DyaL28XmtVClt70%3D
L Kohout M Strnad (1989) ArticleTitleBrassinolide analogues without side chain. Collect Czech Chem Commun 54 1019–1027 Occurrence Handle1:CAS:528:DyaK3cXnslym
L Kohout M Strnad M Kaminek (1991) Types of brassinosteroids and their bioassays. HG Cutler T Yokota G Adam (Eds) Brassinosteroids: chemistry, bioactivity and applications. ACS Sym Ser 474. American Chemical Society Washington, DC 56–73
W Luo L Janzen RP Pharis TG Back (1998) ArticleTitleBioactivity of brassinolide methyl ethers. Phytochemistry 49 637–642 Occurrence Handle10.1016/S0031-9422(97)00881-9 Occurrence Handle1:CAS:528:DyaK1cXmsF2qtLg%3D
NB Mandava (1988) ArticleTitlePlant growth-promoting brassinosteroids. Ann Rev Plant Physiol Plant Mol Biol 39 23–52 Occurrence Handle10.1146/annurev.pp.39.060188.000323 Occurrence Handle1:CAS:528:DyaL1cXlsVKhtrY%3D
TC McMorris (1999) Chemical synthesis of brassinosteroids. A Sakurai T Yokota SD Clouse (Eds) Brassinosteroids: steroidal plant hormones. Springer-Verlag Tokyo 69–90
K Mori T Takeuchi (1988) ArticleTitleSynthesis of 25-methyldolichosterone, 25-methyl-2,3-diepidolichosterone, 25-methylcastasterone and 25-methylbrassinolide. Liebigs Ann Chem . 815–818
K Okada K Mori (1983) ArticleTitleSynthesis of brassinolide analogs and their plant growth-promoting activity. Agric Biol Chem 47 89–95 Occurrence Handle1:CAS:528:DyaL3sXitFaqsbg%3D
RP Pharis L Janzen SK Nakajima J Zhu TG Back (2001) ArticleTitleBioactivity of of 25-hydroxy, 26-hydroxy, 25,26-dihydroxy- and 25,26-epoxybrassinolide. Phytochemistry 58 1043–1047 Occurrence Handle10.1016/S0031-9422(01)00381-8 Occurrence Handle1:CAS:528:DC%2BD3MXos1Wrsbw%3D Occurrence Handle11730867
JA Ramírez EG Gros LR Galagovsky (2000) ArticleTitleEffects on bioactivity due to C-5 heteroatom substituents on synthetic 28-homobrassinosteroid analogs. Tetrahedron 56 6171–6180 Occurrence Handle1:CAS:528:DC%2BD3cXlvVKksrg%3D
A Sakurai T Yokota SD Clouse (Eds) (1999) Brassinosteroids: steroidal plant hormones. Springer-Verlag Tokyo
JM Sasse (1991) The case for brassinosteroids as endogenous plant hormones. HG Cutler T Yokota G Adam (Eds) Brassinosteroids: chemistry, bioactivity and applications. ACS Symp Ser 474. American Chemical Society Washington, DC 158–166
B Schneider A Kolbe A Porzel G Adam (1994) ArticleTitleA metabolite of 24-epibrassinolide in cell suspension cultures of Lycopersicon esculentum. Phytochemistry 36 319–321 Occurrence Handle10.1016/S0031-9422(00)97068-7 Occurrence Handle1:CAS:528:DyaK2cXksFCjsL8%3D
H Seto S Fujioka H Koshino T Suenaga S Yoshida T Watanabe S Takatsuto (1998) ArticleTitleEpimerization at C-5 of brassinolide with sodium methoxide and the biological activity of 5-epibrassinolide in the rice leaf lamina inclination test. J Chem Soc Perkin Trans 1 3355–3358 Occurrence Handle10.1039/a805945d
H Seto S Fujioka H Koshino H Hayasaka T Shimizu S Yoshida T Watanabe (1999a) ArticleTitleSynthesis and biological activity of 6a-carbabrassinolide: B-ring homologation of 6-oxo-steroid to 6-oxo-7a-homosteroid with trimethylsilyldiazomethane-boron trifluoride etherate. Tetrahedron Lett 40 2359–2362 Occurrence Handle1:CAS:528:DyaK1MXhvVemt7c%3D
H Seto S Fujioka H Koshino T Suenaga S Yoshida T Watanabe S Takatsuto (1999b) ArticleTitle2,3,5-Tri-epi-brassinolide: preparation and biological activity in rice leaf lamina inclination test. Phytochemistry 52 815–818 Occurrence Handle1:CAS:528:DC%2BD3cXhtFequg%3D%3D
H Seto S Fujioka H Koshino S Yoshida M Tsubuki T Honda (1999c) ArticleTitleSynthesis and biological evaluation of extra-hydroxylated brassinolide analogs. Tetrahedron 55 8341–8352 Occurrence Handle1:CAS:528:DyaK1MXksVSgurc%3D
H Seto S Hiranuma S Fujioka H Koshino T Suenaga S Yoshida (2002) ArticleTitlePreparation, conformational analysis, and biological evaluation of 6a-carbabrassinolide and related compounds. Tetrahedron 58 9741–9749 Occurrence Handle10.1016/S0040-4020(02)01247-4 Occurrence Handle1:CAS:528:DC%2BD38XovVSmur0%3D
GCY Sung L Janzen RP Pharis TG Back (2000) ArticleTitleSynthesis and bioactivity of 6α- and 6β-hydroxy analogues of castasterone. Phytochemistry 55 121–126 Occurrence Handle10.1016/S0031-9422(00)00259-4 Occurrence Handle1:CAS:528:DC%2BD3cXntF2js74%3D Occurrence Handle11065287
S Takatsuto N Yazawa N Ikekawa T Takematsu Y Takeuchi M Koguchi (1983) ArticleTitleStructure–activity relationship of brassinosteroids. Phytochemistry 22 2437–2441 Occurrence Handle10.1016/0031-9422(83)80135-6 Occurrence Handle1:CAS:528:DyaL2cXhsFeqsrw%3D
S Takatsuto N Ikekawa T Morishita H Abe (1987) ArticleTitleStructure–activity relationship of brassinosteroids with respect to the A/B ring functional groups. Chem Pharm Bull 35 211–216 Occurrence Handle1:CAS:528:DyaL2sXktVClsL4%3D
S Takatsuto T Yokota (1999) Biochemical analysis of natural brassinosteroids. A Sakurai T Yokota SD Clouse (Eds) Brassinosteroids: steroidal plant hormones Springer-Verlag Tokyo 47–68
K Takeno RP Pharis (1982) ArticleTitleBrassinosteroid-induced bending of the leaf lamina of dwarf rice seedlings: an auxin-mediated phenomenon. Plant Cell Physiology 23 1275–1281 Occurrence Handle1:CAS:528:DyaL3sXivVal
MJ Thompson WJ Meudt NB Mandava SR Dutky WR Lusby DW Spaulding (1982) ArticleTitleSynthesis of brassinosteroids and relationship of structure to plant growth-promoting effects. Steroids 39 89–l05 Occurrence Handle10.1016/0039-128X(82)90129-5 Occurrence Handle1:CAS:528:DyaL38XlvFynt78%3D Occurrence Handle7080117
B Voigt A Porzel D Golsch W Adam G Adam (1996) ArticleTitleRegioselective oxyfunctionalization of brassinosteroids by methyl(trifluoromethyl)dioxirane: synthesis of 25-hydroxybrassinolide and 25-hydroxy-24-epibrassinolide by direct C-H insertion. Tetrahedron 52 10653–10658 Occurrence Handle10.1016/0040-4020(96)00587-X Occurrence Handle1:CAS:528:DyaK28XkvV2ksrc%3D
K Wada S Marumo (1981) ArticleTitleSynthesis and plant growth-promoting activity of brassinolide analogues. Agric Biol Chem 45 2579–2585 Occurrence Handle1:CAS:528:DyaL38XotFWrug%3D%3D
T Yokota K Mori (1992) Molecular structure and biological activity of brassinolide and related brassinosteroids. M Bohl WL Duax (Eds) Molecular structure and biological activity of steroids CRC Press Boca Raton, FL 317–340
T Yokota Y Ogino H Suzuki N Takahashi H Saimoto S Fujioka A Sakurai (1991) Metabolism and biosynthesis of brassinosteroids. HG Cutler T Yokota G Adam (Eds) Brassinosteroids: chemistry, bioactivity and applications. ACS Symp Ser 474. American Chemical Society Washington, DC 86–96
Acknowledgements
We thank the Natural Sciences and Engineering Research Council of Canada (Research, Strategic, and CRD grants), the Environmental Science and Technology Alliance of Canada, Agritope Inc. (now Exelixis Plant Sciences Inc.), and CIDtech Research Inc. for financial support.
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Back, T.G., Pharis, R.P. Structure–Activity Studies of Brassinosteroids and the Search for Novel Analogues and Mimetics with Improved Bioactivity . J Plant Growth Regul 22, 350–361 (2003). https://doi.org/10.1007/s00344-003-0057-0
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DOI: https://doi.org/10.1007/s00344-003-0057-0