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Chemoselective O-methylation of N-acylated/sulfonylated tyrosine derivatives

✍ Scribed by Mireille Attolini; Thierry Boxus; Stéphane Biltresse; Jacqueline Marchand-Brynaert

Publisher
Elsevier Science
Year
2002
Tongue
French
Weight
50 KB
Volume
43
Category
Article
ISSN
0040-4039

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✦ Synopsis

Methyl ethers (6a and 6b) of N-trifluoroacetyl-and N-(m-trifluoromethyl) phenylsulfonyl-6-nitro-tyrosine t-butyl ester were readily prepared by modified Mitsunobu reaction (DPPE, DIAD, MeOH). Williamson (MeI, K 2 CO 3 or Li 2 CO 3 or NaOH under phase transfer) and classical Mitsunobu conditions (PPh 3 , DEAD, MeOH) gave O,N-dimethylated derivatives (7a and 7b) as side or main products. O-versus N-selectivity in tyrosine methylation reactions depends on both pK a values and steric factors.

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