Strigolactones: Plant Hormones with Promising Features

Abstract

Almost 80 years after the discovery of the first plant hormone, auxin, a few years ago a new class of plant hormones, the strigolactones, was discovered. These molecules have unprecedented biological activity in a number of highly important biological processes in plants but also outside the plant in the rhizosphere, the layer of soil surrounding the roots of plants and teeming with life. The exploitation of this amazing biological activity is not without challenges: the synthesis of strigolactones is complicated and designing the desired activity a difficult task. This minireview describes the current state of knowledge about the strigolactones and how synthetic analogs can be developed that can potentially contribute to the development of a sustainable agriculture.

Total Synthesis and Biological Evaluation of Zealactone 1a/b

“…The mixture was stirred for 22 h at room temperature. An aqueous saturated solution of NH 4 Cl (30 mL), acetic acid (2.0 mL) and dichloromethane (50 mL) were added, the aqueous layer was extracted with dichloromethane (4 × 50 mL), the combined organic layers were dried over MgSO 4 (24). To a solution of acid 16 (2.50 g, 10.5 mmol, 1.00 equiv.)…”

“…All these positive effects play a pivotal role in the promotion of sustainable agriculture. [4][5][6][7] Therefore, strigolactones represent a promising starting point to develop innovative technologies with potential applications for a more sustainable crop production. In nature, several plant species synthesize specific strigolactones.…”

Total Synthesis and Biological Evaluation of Heliolactone

“…Strigolactones play a surprisingly broad role to help many crops to deal with drought stress, early crop development under low temperatures and nutrient assimilation. All these positive effects make strigolactones an interesting technology to promote sustainable agriculture . Since the first isolation of a strigolactone, namely (+)‐strigol ( 1 ), from the root exudates of cotton in 1966, diverse structures of strigolactones have been isolated from a variety of plant species ( Figure ) .…”

“…[12,13] Carlactonic acid (CLA; 3) and methyl carlactonoate (MeCLA; 4), which are the first-discovered non-canonical strigolactones, are synthesized from CL (2) in planta, and show strigolactone-like activity through the interaction with a specific receptor protein, DWARF14 (D14). [14] Besides, avenaol (6), [15] zealactone (7), [16] zeapyranolactone (9) [17] and heliolactone (10) [18] have been discovered as non-canonical strigolactones from avena, corn and sunflower, respectively. These crops exclusively produce non-canonical strigolactones as the most abundant strigolactones, which suggest that non-canonical strigolactones might contribute the growth and development of field crops.…”

“…[19] Very recently, McErlean and coworker reported a total synthesis of heliolactone by Stille cross-coupling. [20] The spectroscopic analysis of synthetic heliolactone enabled to clear up the issue of stereochemical ambiguity at C (6) (Figure 1). In parallel with their work, we performed the synthesis of helio-lactone through the Stille cross-coupling reaction we developed previously.…”