- Advantage of in situ generation of N-arylsulfonyl imines from α-amide sulfones in the phase-transfer-catalyzed asymmetric Strecker reaction
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Highly efficient, catalytic enantioselective synthesis of N-arylsulfonyl α-amino nitriles from the corresponding α-amido sulfones has been achieved under toluene-aqueous potassium cyanide biphasic conditions using chiral quaternary ammonium iodide (R,R,R)-1 as an effective phase-transfer catalyst. This Strecker synthesis involving the in situ generation of the reactive N-sulfonyl imines is advantageous for the cyanation of the substrates having primary and secondary alkyl substituents.
- Ooi, Takashi,Uematsu, Yukitaka,Fujimoto, Jun,Fukumoto, Kazuhiro,Maruoka, Keiji
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p. 1337 - 1340
(2007/10/03)
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- Method for protecting amino group and restoring the same
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An ω-amino group and/or α-amino group in an amino acid or a peptide can be protected with a 4-methoxy-2,3,6-trimethylbenzenesulfonyl group, and said group may easily be removed without affecting the amino acid or the peptide. Thus, the present invention is useful in the synthesis of peptide containing ω-amino group and/or α-amino group.
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- Method for protecting guanidino group and restoring the same
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A guanidino group in an amino acid or a peptide can be protected with a specific group, i.e. pentamethylbenzensulfonyl, 2,4,6-trimethoxybenzenesulfonyl, 4-methoxy-2,3,5,6-tetramethylbenzenesulfonyl, 4-methoxy-2,6-dimethylbenzenesulfonyl or 4-methoxy-2,3,6-trimethylbenzenesulfonyl, and said group may easily be removed without affecting the amino acid or the peptide to be derived from the protected amino acid or peptide. Thus, the present invention is useful in the synthesis of peptides containing the guanidino group.
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- Further Studies on the Use of Multi-substituted Benzenesulfonyl Groups for Protection of the Guanidino Function of Arginine
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Various multi-substituted benzenesulfonyl protecting groups for the guanidino function of arginine, removable under mild conditions such as with trifluoroacetic acid (TFA)-thioanisole, were studied.Among them, the 4-methoxy-2,6-dimethylbenzenesulfonyl (Mds) group, the 2,3,4,5,6-pentamethylbenzenesulfonyl (Pme) group, and the 4-methoxy-2,3,6-trimethylbenzenesulfonyl (Mtr) group were found to be useful.Both Mds and Pme show considerable resistance to TFA and, therefore, are suitable for procedures in which the intermediates are deprotected by TFA treatment, while Mtr is the most useful protecting group when TFA treatment is not necessary.Keywords---4-methoxy-2,6-dimethylbenzenesulfonyl (Mds); 2,4,6-trimethoxybenzenesulfonyl (Mtb); 2,3,4,5,6-pentamethylbenzenesulfonyl (Pme); 4-methoxy-2,3,6-trimethylbenzenesulfonyl (Mtr); trifluoroacetic acid-thioanisole deprotection
- Fujino, Masahiko,Wakimasu, Mitsuhiro,Kitada, Chieko
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p. 2825 - 2831
(2007/10/02)
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