Suguru Takatsuto

Structure-activity relationship of brassinosteroids

Abstract The plant growth-promoting activities of brassinolide and brassinosteroids with different side chains were investigated by means of the Raphanus an

Microanalysis of brassinolide and its analogues by gas chromatography and gas chromatography-mass spectrometry

Abstract The microanalysis of brassinolide, a new plant growth promotor, was investigated using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Bismethaneboronate was found to be a suitable derivative for analysis of brassinolide and its analogues by gas-phase analysis. GC and GC-MS analysis of the derivative are useful for identification and screening of brassinolide in plants.

Analysis of natural brassinosteroids by gas chromatography and gas chromatography-mass spectrometry

The microanalysis of various kinds of brassinosteroids as their bismethaneboronate derivatives was investigated by gas chromatography (GC) and gas chromatography—mass spectrometry (GC—MS). GC analysis using a glass capillary column indicated that the brassinosteroid methaneboronates can be detected at the nanogram level. The fragmentation patterns of the bismethaneboronate derivatives of brassinosteroids were examined using GC—EI (electron impact)-MS and GC—CI (chemical ionization)-MS systems. Selected ion monitoring using the GC—CI-MS system was applied to the analysis of natural brassinosteroids in several plants. Brassinolide, castasterone, 28-norbrassinolide, brassinone, 24-ethylbrassinone and dolichosterone were identified in the immature needs and sheaths of chinese cabbage, Brassica campestris L. var. pekinensis, the leaves of green tea, Thea sinensis, the insect galls of the chesnut tree, Castanea crenata L. Sieb. et Zucc., the insect galls and the leaves of Distylium racemosum Sieb. et Zucc. and the whole plant except the roots of the rice, Oryza sativa L. cv. Arborio J1. The results demonstrate that this microanalysis is useful for the screening of brassinosteroids in plants.

Synthesis of (24R)-28-homobrassinolide analogues and structure-activity relationships of brassinosteroids in the rice-lamina inclination test

Abstract In order to investigate the biological importance of the alkyl group at the C-24 position of brassinolide, four (24 R )-28-homobrassinofide analogues were synthesized from poriferasterol. The plant growth-promoting activity of brassinosteroids with a 24-methyl, -ethyl, or -hydrogen was examined by the rice-lamina inclination test. Structure-activity relationships of brassinosteroids with respect to the stereochemistry of the side chain were also investigated in this bioassay system. The results indicate that an S-configuration of the alkyl group at C-24, a cis -configuration of the C-22, C-23 vicinal diol, and the A,B-ring functionalities of brassinolide are structural requirements for significant plant growth-promoting activity.

Synthesis and biological activity of brassinolide analogues, 26,27-bisnorbrassinolide and its 6-oxo analogue

Abstract Two hitherto unknown brassinolide analogues, (22 R ,23 R )-2α,3α,22,23-tetrahydroxy- B -homo-7-oxa-24-nor-5α-cholestan-6-one ( 9b ) and (22 R ,23 R )-2α,3α,22,23-tetrahydroxy-24-nor-5α-cholestan-6-one ( 8a ), were stereoselectively synthesized. In both the Raphanus and rice-lamina inclination tests, 9b exhibited almost the same activity as brassinolide ( 1 ) and 8a also showed ca 10–50% of the activity of 1 .

Remote substituent effect on the regioselectivity in the baeyer-villiger oxidation of 5α-cholestan-6-one derivatives

Abstract The regioselectivity in the Baeyer-Villiger oxidation of 5α-cholestan-6-one derivatives was markedly affected by the substituents at C-1, 2 or 3 position which were located at γ or δ position from the reaction center c-6.

Stereoselective synthesis of plant growth-promoting steroids, dolicholide and 28-norbrassinolide

Abstract Stereoselective introduction of (22R, 23R)-vicinal diol function at C-22, C-23 position of the steroidal side chain was achieved using the method of chelation control, leading to the stereoselective synthesis of dolicholide (4) and 28-norbrassinolide (2)