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Iridoids, XXI. Synthesis of [ 13 C]Secologanin
Author(s) -
Tietze Lutz F.,
Henke Stephan,
Remberg Gerd
Publication year - 1986
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.198619860813
Subject(s) - chemistry , acetal , yield (engineering) , aldehyde , catalysis , diol , organic chemistry , total synthesis , stereochemistry , medicinal chemistry , materials science , metallurgy
Acid‐catalyzed reaction of natural secologanin ( 1 ) with ethylene glycol to 5a , followed by acetylation gave the peracetylated acetal 5b in almost quantitative yield. Oxidation of 5b with equimolar or catalytic amounts of osmium tetraoxide afforded stereoselectively the diol 6 as main product (31% resp. 28%) besides recovered starting material. 5b was cleaved with lead tetraacetate to give 96% of the aldehyde 10 . Reaction of 10 with triphenylphosphonio‐[ 13 C]methanide led to the labelled secologanin derivative [10‐ 13 C]‐ 5b and the pyran 12 in a 27% and 52% yield, respectively. Acid‐catalyzed transacetalization of [10‐ 13 C]‐ 5b to [10‐ 13 C]‐ 5c , base‐catalyzed solvolysis of the acetate groups to [10‐ 13 C]‐ 5d and subsequent acid‐catalyzed cleavage of the acetal gave [10‐ 13 C]secologanin ([10‐ 13 C]‐ 1 ). To determine its configuration at C‐9, 6 was transformed via 8a to the tricyclic system 8d , which was independently synthesized via a photocycloaddition of the galactose derivative 13 and diformylacetate 14 .