Extracts of Brassica napus L. (rape) pollen (family, Cruciferae) have been reported to produce a novel growth-promoting effect when applied to young pinto bean plants1,2. Fractions that are active in the bean second-internode assay3 give rise to both increased cell elongation and cell division4. The validity of these early reports has been questioned because biological activity was not correlated with any one pure compound5. Subsequently, we showed that isolation of the growth promoter was complicated by the presence of chromatographically similar, inactive components that were identified as 6-D-glucopyranosyl esters of long-chain fatty acids6. We now report the isolation, structure determination and biological activity of this new plant growth promoter, named (22R, 23R, 24S)-2α-3α,22,23-tetrahydroxy-24-methyl-6,7-s-5α-cholestano-6,7-lactone or brassinolide (Fig. 1).

Brassinolide, a plant growth-promoting steroid isolated from Brassica napus pollen

The structures of the title compounds have been established by X-ray crystal structure analysis, based on three-dimensional diffractometer data. Bond lengths and angles are given, and the thermal motion of the molecules in the crystals is discussed. The most striking feature of all three molecules is the twist of the aniline ring out of the CNCC plane by 41–55°.

Crystal and Molecular Structures of Benzylideneaniline, Benzylideneaniline-p-carboxylic acid and p-methylbenzylidene-p-nitroaniline

Photoreactions of cyclic imides. Examples of synthetic organic photochemistry

The prediction and synthesis of new crystal structures enable the targeted preparation of materials with desired properties. Among porous solids, this has been achieved for metal-organic frameworks ...

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A zeolite family with expanding structural complexity and embedded isoreticular structures

The structure and absolute configuration of Chaetocin, a metabolite of the fungus Chaetomium minutum with antibacterial and cytostatic activity has been elucidated by chemical and X-ray methods.

J. Karle

Papers

The symbolic addition procedure for phase determination for centrosymmetric and non‐centrosymmetric crystals