Synthese von zwei natürlich vorkommenden Lactonen mit 10gliedrigen Ringen: (±)-Phoracantholid J und I
✍ Scribed by Hans Gerlach; Peter Künzler; Konrad Oertle
- Publisher
- John Wiley and Sons
- Year
- 1978
- Tongue
- German
- Weight
- 366 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Synthesis of Two Naturally Occurring 10‐Membered Ring Lactones: (±)‐Phoracantholide J and I
Two 10‐membered ring lactones 7 and 11 from the metasternal secretion of the eucalypt longicorn Phoracantha synonyma have been synthesized by the following method. Reaction of the dilithium derivative of 4‐pentynoic acid (3) with 4‐tetrahydropyranyloxy‐1‐pentylbromide (2), followed by removal of the protecting group and by esterification with diazomethane, gave methyl 9‐hydroxy‐4‐decynoate (4; s. Scheme 1). Partial hydrogenation of the triple bond in 4 with Lindlar palladium catalyst, followed by saponification lead to cis‐9‐hydroxy‐4‐decenoic acid (6). The 9‐hydroxydecanoic acid (9) was synthesized by addition of methyl magnesium iodide to methyl 8‐formyloctanoate (8) followed by saponification (s. Scheme 2). The hydroxy acids 6 and 9 were converted into the S‐(2‐pyridyl) thioesters and cyclized in dilute benzene solution under the influence of silver ions to yield (±)‐phoracantholide J (7) and I (11) in 74 and 71% yield, respectively.