10.1271/bbb.68.1097
The research details a study on the synthesis and evaluation of brassinosteroids, plant hormones known for their role in cell elongation and division, which are crucial for plant growth and stress resistance. The purpose of the study was to synthesize various brassinosteroids with different acyl side chains and assess their brassinolide-like activity, using the rice lamina inclination assay with synergist indole-3-acetic acid (IAA). The researchers concluded that the introduction of a hydroxyl group in the α-position to the carbonyl group of the ester structure significantly enhanced the activity, with 2β,3β-dihydroxy-17β-[(2R,3S)-2hydroxy-3-methylpentanoyl]oxy-B-homo-7-oxa-5β-androstan-6-one showing the highest activity. The study also found that the R-form of the acyl moiety was more potent than the S-form and that modifying the terminal structure did not increase activity. Chemicals used in the synthesis process included various steroidal compounds like pregnenolone and stigmasterol, as well as a range of reagents such as dicyclohexylcarbodiimide (DCC), dimethylaminopyridine (DMAP), and protective groups like tert-butyldiphenylsilyl (TBDPS).
10.1021/acs.joc.0c00542
The research focuses on the development of an efficient method for the synthesis of seven-membered biaryl lactams through a Pd-catalyzed, native amine-directed ortho-arylation of benzylamines followed by in situ lactamization. This one-pot cascade reaction employs 2-iodobenzoates and is characterized by a broad substrate scope and good functional group tolerance. The study explores the use of ester versus carboxylic acid-functionalized coupling partners and investigates the potential for synthesizing eight-membered biaryl lactams. The researchers successfully demonstrated the versatility of the method, which includes the synthesis of various biaryl lactams and their derivatives, and potential applications in natural product synthesis, such as accessing the aza-brassinolide core. Key chemicals used in the process include Pd(OAc)2 as a catalyst, AgOAc as an additive, and a variety of benzylamines and 2-iodobenzoate esters as substrates. The conclusions highlight the robustness of the protocol, which works with α-tertiary, α-secondary, and α-primary amines, and its potential use as an entry into natural product synthesis, without the need for CO2 or other transient directing groups.
10.1016/S0040-4039(00)99185-8
The research presents a novel method for synthesizing the side chain of brassinolide, a plant growth regulator. The primary purpose of this study was to develop a stereocontrolled synthesis of the brassinolide side chain, which is challenging due to the presence of four contiguous chiral centers. The researchers utilized pyranone derivatives as versatile intermediates to achieve this goal. Key chemicals involved in the synthesis include 20-carboxaldehyde, Z-lithiofuran, pyridinium chlorochromate, ethoxyethyl ethers, lithium dimethylcuprate, lithium diisopropylamide, methyl iodide, sodium borohydride, lithium aluminum hydride, methanesulfonyl chloride, and acetic anhydride. The study successfully demonstrated a stereocontrolled synthesis route, starting from the addition of Z-lithiofuran to 20-carboxaldehyde to produce furylcarbinols, followed by a series of oxidation, reduction, and protection steps to construct the pyranone derivative. Subsequent reactions, including conjugate addition and selective methylation, led to the formation of the desired side chain. The final conversion of the synthesized side chain into brassinolide was achieved through a series of known steps, thus completing the formal synthesis of brassinolide. The conclusions highlight the effectiveness of using pyranone derivatives as intermediates for the stereocontrolled synthesis of complex polyhydroxylated steroid side chains, providing a new and efficient method for constructing the brassinolide side chain.
