Oxidation of Alkylidenetriphenylphosphoranes with Phosphite-Ozone Adducts

✍ Scribed by Prof. Dr. Hans Jürgen Bestmann; Dipl.-Chem. Lothar Kisielowski; Dr. Werner Distler

• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: English
• Weight: 213 KB
• Volume: 15
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.197602981

✦ Synopsis

is removed with trifluoroacetic acid (TFA/CH2C12, 1 : 1 ; yield 5.9 g = 70 % as TFA derivative).

In analogy to the above two peptide linkages the protected pentapeptide Boc-L-Tyr(Bz1)-Gly-Gly-L-Phe-L-Met-OMe (1.2 g, 77 % yield) was obtained from Boc-L-Tyr(Bz1)-Gly-Gly-O H (1 g, 2 mmol) and H -L -P ~~-L -M ~~-O M ~. C F , C O O H (0.85 g, 2 mmol). Twelve hours' hydrolysis of the methyl ester at room temperature in methanol/water (1 : 1) at pH 12.5 (adjusted with 1 N NaOH), neutralization with 1 N HCI, and evaporation was followed by removal of the remaining protectinggroup with HF in the presence of anisole, and precipitation of the peptide with ether. An aqueous solution of the peptide was then stirred for 90min with Dowex 1 x 8 (OH form). After the resin had been filtered off the peptide was recrystallized from ether/alcohol mixtures (yield 540mg= 61 %): The purity was established by thin layer chromatography (silica gel plates (F254) from Merck, mobile phase : n-butanol/glacial acetic acid/water (3 : 1 : I), Rf = 0.42).

Methionine-enkephalin melts and decomposes at 195°C; its rotatory power [a]&% +31.5" (c=0.96, MeOH).