203798-85-0

Upstream product

• 203571-41-9 3,4-dibenzyloxycinnamoyl chloride 
• 203798-74-7 (R)-methyl 3-(3,4-bis(benzyloxy)phenyl)-2-hydroxypropanoate 
• 100-44-7 benzyl chloride 
• 136749-45-6 (+)-(S)-methyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate 
• 203798-72-5 Benzoic acid (R)-2-(3,4-bis-benzyloxy-phenyl)-1-methoxycarbonyl-ethyl ester 
• 203798-70-3 (S)-3-(3,4-Bis-benzyloxy-phenyl)-2-hydroxy-propionic acid methyl ester 
• 100-39-0 benzyl bromide 
• 99353-00-1 rosmarinic acid methyl ester 

Downstream Products

• 1246887-09-1 C₂₃H₂₂O₅ 
• 71038-25-0 methyl (E)-3-(3,4-bis(benzyloxy)phenyl)acrylate 
• 203798-74-7 (R)-methyl 3-(3,4-bis(benzyloxy)phenyl)-2-hydroxypropanoate 
• 99353-00-1 rosmarinic acid methyl ester 

Relevant academic research and scientific papers

Explorations of caffeic acid derivatives: Total syntheses of rufescenolide, yunnaneic acids C and D, and studies toward yunnaneic acids A and B

Yunnaneic acids A-D, isolated from the roots of Salvia yunnanensis, are hexameric (A and B) and trimeric (C and D) assemblies of caffeic acid that feature an array of synthetically challenging and structurally interesting domains. In addition to being caffeic acid oligomers, yunnaneic acids A and B are formally dimeric and heterodimeric adducts of yunnaneic acids C and D. Herein we report the first total syntheses of yunnaneic acids C and D featuring the formation of their bicyclo[2.2.2]octene cores in a single step from simple precursors via an oxidative dearomatization/Diels-Alder cascade that may have biogenetic relevance. In addition, exploitation of the key intermediate resulting from this cascade reaction has enabled rapid access to the structurally related caffeic acid metabolite rufescenolide through an unexpected Lewis acid-mediated reduction. Finally, we report the results of extensive model studies toward forming the dimeric yunnaneic acids A and B. These explorations indicate that the innate reactivities of the monomeric fragments do not favor spontaneous formation of the desired dimeric linkages. Consequently, enzymatic involvement may be required for the biosynthesis of these more complex family members.

Synthesis of enantiomeric (+)- and (-)-rosmarinic acid methylesters

Starting from L-tyrosine (L-1), the phenyl lactic acid ester (-)-4 was prepared by reported procedures. (-)-4 could then be converted to the benzyl ether (-)-5. From (-)-5, the corresponding optical antipode (+)-5 is available via (+)-6 by Mitsunobu reaction. The enantiomeric excess of 5 was determined by NMR spectroscopy from camphanic acid esters (+)- and (-)-8, respectively. The phenyl lactic acid esters (+)- and (-)-5 were acylated by caffeoyl chloride (9) to yield the O-protected enantiomeric rosmarinic acid esters (+)- and (-)-10. Deprotection of 10 by BCl3 afforded the title compounds (+)- and (-)-11 in fair yields.