Synthesis of [13C]- and [2H]betulin for biological transformations

✍ Scribed by Tietze, Lutz F. ;Heinzen, Horacio ;Moyna, Patrick ;Rischer, Matthias ;Neunaber, Horst

• Book ID: 102902320
• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 534 KB
• Volume: 1991
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.1991199101215

✦ Synopsis

Abstract

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).