57458-00-1

Upstream product

• 29938-06-5 2-(Benzyloxy)-1,4-benzoquinone 
• 4043-71-4 isosafrole 
• 1446-24-8 3-allylphenol 
• 58095-76-4 (E)-3-(benzo[d][1,3]dioxol-5-yl)prop-2-en-1-ol 
• 74-88-4 methyl iodide 
• 87402-78-6 Liliflol A 
• 147915-99-9 2-Allyl-5-(benzyloxy)-1,4-benzoquinone 

Relevant academic research and scientific papers

Burchellin and its stereoisomers: Total synthesis, structural elucidation and antiviral activity

Burchellin and its analogues are a class of neolignan natural products containing a rare core with three contiguous stereogenic centers. In previous reports, racemic burchellin was synthesized without accessing each of the enantiomers. In this paper, a concise and efficient total synthetic route to divergently access the enantiomers of burchellin and those of its 1′-epi-diastereoisomer over six steps for each is disclosed, where each of the enantiomers was obtained by preparative chiral phase HPLC purification. The key steps include the construction of a 2,3-dihydrobenzofuran moiety by two Claisen rearrangements and a one-step rearrangement/cyclization and subsequent tandem ester hydrolysis/oxy-Cope rearrangement/methylation to furnish the basic skeleton of burchellin. The structures and absolute configurations of the four stereoisomers were determined using spectroscopic data analyses and comparison of experimental and calculated electronic circular dichroism data. These stereoisomers were found to have potent antiviral effects against coxsackie virus B3, and is the first time that bioactivity has been reported for these compounds. This journal is

Regioselective Lewis acid-directed reactions of 2-alkoxy-5-alkyl-1,4-benzoquinones with styrenes: Synthesis of burchellin and guianin neolignans

Reactions of 2-carbomethoxy-5-methoxy-1,4-benzoquinone with (E)-propenylbenzenes promoted by Ti(IV) regio- and stereoselectively yield trans 2-aryl-4-carbomethoxy-7-methoxy-3-methyl-2,3-dihydro-5-benzofuranols. However, the products found in Lewis acid-promoted reactions of 2-alkoxy-5-alkyl-1,4-benzoquinones with (E)-propenylbenzenes depend on the nature of the Lewis acid. Low-temperature reactions with SnCl4 produce rel-(1R,6S,7S,8R)-4-alkoxy-1-alkyl-7-aryl-8-methylbicyclo[4.2.0]oct-3- ene-2,5-diones 21-23 and products derived from them. Allowing the reactions to warm to room temperature results in rel-(2S,3S,3aR)-3a-alkyl-2-aryl-5-hydroxy-3-methyl-2,3,3a,6-tetrahydro -6-oxobenzofurans as mixtures of keto-enol tautomers 26/27 and 28/29. With Ti(IV) as promoter, the reactions can be made to produce either 21-23 or the regioisomeric rel-(1S,6R,7R,8S)-4-alkoxy-1-alkyl-8-aryl-7-methylbicyclo[4.2.0]oct-3- ene-2,5-diones 18-20. The ratio of the two depends upon the makeup of the Ti(IV) promoter and the substituents on the propenylbenzene. A mechanistic rationale is presented involving regioselective coordination of the different Lewis acids to the quinone. Thus, SnCl4 binds to the C-1 carbonyl and C-2 alkoxy oxygens, forming a complex possessing a 2-alkoxy-5-alkyl-4-oxo-2,5-cyclohexadienyl carbocation moiety (e.g. 30) which undergoes a thermally allowed 4π + 2π (5 + 2) cycloaddition with propenylbenzene to give a bicyclo[3.2.1]octenyl carbocation 31; this cation then rearranges to the observed products. On the other hand, the Ti(IV)-promoted reactions give either bicyclo[3.2.1]octenyl carbocation 31 or 34, depending upon reaction conditions, followed by rearrangement. Cyclobutanes 18-20 undergo protic acid rearrangement to give trans 7-alkoxy-4-alkyl-2-aryl-3-methyl-2,3-dihydro-5-benzofuranols 15-17, whereas cyclobutanes 21-23 yield 5-alkyl-7-aryl-3-hydroxy-6-methylbicyclo[3.2.1]oct-3-ene-2,8-diones 24/25. The reactions provide an efficient and stereoselective route to neolignans of the guianin and burchellin classes.

STEREOSELECTIVE SYNTHESES OF THREE DIFFERENT CLASSES OF NEOLIGNANS FROM THE SAME STARTING MATERIALS

Lewis Acid catalyzed reactions of 2-alkoxy-5-allyl-1,4-benzoquinones with styrenes can be manipulated to form either the burchellin or guianin neolignans, or 4-allyl-2-aryl-3-methyl-2,3-dihydrobenzofurans.