The thio-Mitsunobu reaction: a useful tool for the preparation of 2,5-anhydro-2-thio- and 3,5-anhydro-3-thiopentofuranosides.
The unprotected methyl L-arabinofuranosides, D-ribofuranosides and D-xylofuranosides are transformed into the corresponding S-acetyl-5-thio derivatives by the thio-Mitsunobu reaction. Mesylation and subsequent reaction with sodium hydrogen carbonate led, depending on the configuration of the intermediate, to 2,5-anhydro-2-thio- or 3,5-anhydro-3-thiopentofuranosides. Due to inversion at C-3 or C-2 during the intramolecular nucleophilic displacement the products exhibit L-lyxo-, D-arabino- or D-lyxo-configuration. Analogously, the methyl 2,3-anhydro-D-ribofuranosides yielded 5-thio-S-acetates with intact 2,3-oxirane groups, which were cyclised with sodium hydrogen carbonate by epoxide ring opening and concomitant ring closure to form exclusively 3,5-anhydro-3-thio-D-xylofuranosides. A related 3,5-anhydro-3-seleno-D-lyxofuranoside was obtained by reaction of a 3,5-di-O-mesyl-D-arabinofuranoside with sodium hydrogen selenide. Several X-ray diffraction analyses proved the structures of the products.
5,5'-Dimethyl-3,3'-azoisoxazole as a new heterogeneous azo reagent for esterification of phenols and selective esterification of benzylic alcohols under Mitsunobu conditions.
5,5'-Dimethyl-3,3'-azoisoxazole is used as a new efficient heterogeneous azo reagent for the highly selective esterification of primary and secondary benzylic alcohols and phenols with aliphatic and aromatic carboxylic acids via Mitsunobu protocols. The reaction is highly selective for primary benzylic alcohols versus secondary ones, aliphatic alcohols and also phenols. The isoxazole hydrazine byproduct can be simply isolated by filtration and recycled to its azoisoxazole by oxidation.
Some aspects of the destruction of lysine under conditions of acid and enzymic hydrolysis of protein materials containing carbohydrates.
Kerr, L. M. H., Graham, A. F. & Levvy, G. A. (1948). Biochem. J. 42, 191. Marsh, C. A. (1952). J. chem. Soc. p. 1578. Marsh, C. A. & Levvy, G. A. (1956). Nature, Lond., 178, 589. Marsh, C. A. & Levvy, G. A. (1958). Biochem. J. 68, 610. Moggridge, R. C. G. & Neuberger, A. (1938). J. chem. Soc. p. 745. Morgan, W. T. J. & Elson, L. A. (1934). Biochem. J. 28, 988. Quick, A. J. (1927). J. biol. Chem. 74, 331. Rondle, C. J. M. & Morgan, W. T. J. (1955). Biochem. J. 61, 586. Tsou, K.-C. & Seligman, A. M. (1952). J. Amer. chem. Soc. 74, 5605. Tsou, K.-C. & Seligman, A. M. (1953). J. Amer. chem. Soc. 75, 1042.