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Synthesis of [ 13 C]‐ and [ 2 H]betulin for biological transformations
Author(s) -
Tietze Lutz F.,
Heinzen Horacio,
Moyna Patrick,
Rischer Matthias,
Neunaber Horst
Publication year - 1991
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.1991199101215
Subject(s) - betulin , chemistry , yield (engineering) , medicinal chemistry , iodide , methyl iodide , nuclear chemistry , potassium carbonate , methanol , potassium , solvolysis , organic chemistry , hydrolysis , materials science , metallurgy
Selective acetylation of 1 at C‐28 afforded the monoacetate 2 , which was oxidized to the 3‐oxo compound 8 . H,D exchange at C‐2 in 8 followed by reduction with LiAlH 4 led to [2‐ 2 H]‐betulin ( 5 ). Reduction of 8 with NaBD 4 or LiAlD 4 yielded [3‐ 2 H]betulin ( 6 ) besides different amounts of the respective 3α‐hydroxy compound 7 . For the introduction of a CD 2 or 13 CH 2 unit at C‐29 betulin diacetate 4 was ozonolyzed to give the known compound 10 , which was treated either with CD 2 Br 2 , Zn, and TiCl 4 in THF to yield the [29‐ 2 H 2 ] compound 11 or with [ 13 C]methyltriphenylphosphonium iodide and potassium tert ‐butoxide to afford the [29‐ 13 C]‐labeled compound 11 . Solvolysis of 11 and 13 with methanol and potassium carbonate afforded the desired compounds [29‐ 2 H 2 ]betulin ( 12 ) and [29‐ 13 C]betulin ( 14 ).