Synonyms:
99% *data from raw suppliers
Pyridinium chlorochromate 98% *data from reagent suppliers
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The study investigates a remarkably facile 1,3-diol fragmentation process and its application in the synthesis of a seco-sesquiterpene, specifically ( )-4-(2,2,6-trimethyl-6-vinylcyclohexyl)-2-butanone (8). The key finding is that a benzylic hydroxyl group activated by a 2,6-dimethoxy-4-methylphenyl group acts as a highly reactive nucleofuge under mild conditions. This was demonstrated through the fragmentation of 1,3-diol 1 into ketone 2 and tetrahydrofuran 3 using pyridinium chlorochromate in CH2Cl2. The study also explored the fragmentation of benzyl alcohol 13, derived from drimanic 1,3-diol 9 and aldehyde 10, which readily fragmented to give olefinic ketone 15. This fragmentation product was then used as a synthetic precursor to produce the target seco-sesquiterpene through a series of reactions, including acetal formation, ozonolysis, esterification, reduction, and Wittig reaction, ultimately yielding the desired compound in quantitative yield. The study highlights the efficiency and mild conditions of the fragmentation process, which could be useful in the synthesis of other natural products.
The study presents a chemoenzymatic asymmetric synthesis of (9S,12S,13S)- and (9S,12RS,13S)-pinellic acids, which are significant due to their adjuvant activity for influenza vaccines. The synthesis involves several key steps and chemicals. Initially, 1,9-nonanediol is monoprotected with para-methoxybenzyl chloride (PMBCl) to form compound 3, which is then oxidized with pyridinium chlorochromate (PCC) to yield aldehyde 4. The reaction of 4 with vinylmagnesium bromide produces allylic alcohol 5. A crucial step involves Novozyme 435-catalyzed acetylation of 5 with vinyl acetate, yielding (S)-acetate 6 and (R)-alcohol 5 with high enantiomeric excesses. Another significant component, (R)-cyclohexylideneglyceraldehyde 7, is reacted with CH3(CH2)4Li to form the anti-triol derivative 8, which is then protected with tert-butyldiphenylsilyl chloride (TPSCl) to form silyl derivative 9. The acetal function of 9 is removed to yield diol 10, which is cleaved with NaIO4 to form aldehyde 11. The reaction of 11 with vinylmagnesium bromide produces allylic alcohol 12. A cross-metathesis reaction between (S)-5 and 12, catalyzed by Grubbs 2nd generation catalyst, yields diol 13. Further steps involve silylation, oxidative removal of PMB protection, oxidation to form acid 16, and final desilylation to obtain the target pinellic acids. This method highlights the use of biocatalysis and chiral templates for efficient asymmetric synthesis, offering a simpler and more efficient route to these biologically active compounds.
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.
The study investigates the design and total convergent synthesis of new analogs of cholecalciferol (vitamin D) with the CD-ring system replaced by a two-carbon aliphatic spacer. The researchers aimed to simplify the structure of vitamin D-based therapeutics by identifying the essential structural parts responsible for its activity. The key chemicals involved include vitamin D derivatives, such as vitamin D3 and 1α-hydroxyvitamin D3, which serve as precursors for the ring fragments. The chain fragment is derived from S-(-)-β-citronellol, a natural monoterpene. The synthesized compounds, RAD and RAD2, are designed as des-CD analogs of 25-OH-D3 and 1,25-(OH)2D3, respectively, with an unnatural configuration at C-20. The study employs various reagents and conditions, such as imidazole, t-BuMe2SiCl, MCPBA, lithium triethylborohydride, and pyridinium chlorochromate, to achieve the desired modifications and coupling of the ring and chain fragments. The results provide insights into the potential for developing more effective therapeutic agents based on the simplified structure of vitamin D.
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