Synthesis of hexadeuterated 23-dehydroxybrassinosteroids

Area of Science:

• Plant Steroid Biochemistry
• Organic Synthesis

Background:

• Brassinosteroids (BS) are crucial plant hormones regulating growth and development.
• The biosynthesis pathway of brassinolide, the most active BS, involves several intermediate compounds.
• Specific intermediates with hydroxyl groups at C(22) are critical for understanding brassinolide formation.

Purpose of the Study:

• To synthesize hexadeuterated brassinosteroids ([26,27-2H(6)]-23-dehydroxycastasterone and [26,27-2H(6)]-cathasterone) for biochemical investigations.
• To prepare analogs of brassinosteroid biosynthesis intermediates with a C(22) hydroxyl group.
• To facilitate studies on the brassinolide biosynthetic pathway.

Main Methods:

• Stereoselective synthesis utilizing (2R)-3-hydroxy-2-methylpropanoate as a chiral building block.
• Sulfone chemistry for coupling the side chain to the tetracyclic steroidal core via a C(22) aldehyde.
• Hydride reduction to establish the C(22) hydroxyl group configuration.
• Deuterium incorporation using [2H(3)]methyl iodide for labeling at C(26) and C(27).

Main Results:

• Successful synthesis of two hexadeuterated brassinosteroids, [26,27-2H(6)]-23-dehydroxycastasterone and [26,27-2H(6)]-cathasterone.
• These compounds feature a C(22) hydroxyl group, differing from the typical 22R,23R-diol in many brassinosteroids.
• The synthetic route ensured correct stereochemistry at C(24) and incorporated deuterium labels at C(26) and C(27).

Conclusions:

• The synthesized deuterated compounds serve as valuable tools for biochemical studies of brassinosteroid biosynthesis.
• The methodology provides a reliable pathway for preparing specific brassinosteroid intermediates.
• Further research can utilize these labeled compounds to elucidate the precise mechanisms of brassinolide formation.