[6066-32-6]  · C4H5NO3  · N-Hydroxysuccinimide  · (MW 115.10)

(activating agent for carboxylic acids in amide synthesis and related coupling reactions; acyl transfer reagent)

Alternate Name: HOSu.

Physical Data: mp 96-98 °C (99-100 °C).

Solubility: sol H2O, DMF, alcohols, EtOAc; insol cold ether.

Form Supplied in: colorless crystalline solid, widely available.

Preparative Methods: by heating Succinic Anhydride with Hydroxylamine or, better, hydroxylamine hydrochloride followed by crystallizations from ether, 1-butanol, and finally EtOAc.1

Purification: can be crystallized from 1-butanol, EtOAc, or EtOH-EtOAc.

Peptide Bond Formation.

The most important use of N-hydroxysuccinimide is in the formation of (isolable) activated derivatives of Na-protected a-amino acids, which subsequently undergo generally smooth coupling reactions with amino esters. Typically, 1,3-Dicyclohexylcarbodiimide (DCC) is used as the initial coupling agent (the HOSu-DCC method) (eq 1).1-3 N-Hydroxyphthalimide can be employed in much the same way, but a distinct advantage in the case of HOSu is its high water solubility, which facilitates product purification.

In some cases, up to 3% racemization has been observed when using the HOSu-DCC method, which renders it unsuitable for some types of peptide synthesis.4,5 Esters derived from HOSu are relatively reactive, as shown by a kinetic study of their rates of hydrolysis in aqueous buffers6 although, in some examples, endo-N-hydroxy-5-norbornene-2,3-dicarboximide has proven superior to HOSu in peptide bond formation.7 Of course, the HOSu-DCC method is not limited to peptide synthesis and is well suited to the preparation of amides in general, both from ammonia and primary amines (e.g. eq 2).8

In order to avoid the need for DCC, a number of activated derivatives of N-hydroxysuccinimide itself have been developed which react directly with, for example, an a-amino acid to provide the required activated a-amino acid esters. These include the commercially available carbonate (1), a stable crystalline solid obtained from HOSu and Trichloromethyl Chloroformate or from O-trimethylsilyloxysuccinimide and Phosgene,9 and the related phosphate (2) derived from HOSu and Diphenyl Phosphorochloridate under Schotten-Baumann conditions.10 Another alternative (also commercially available) is the oxalate (3), formed from HOSu and Oxalyl Chloride.11 In general, these intermediates react rapidly with an Na-protected a-amino acid, usually in the presence of a mild base such as pyridine, to provide excellent yields of the required hydroxysuccinimide esters, generally with less racemization than is sometimes associated with the HOSu-DCC method. It is also possible to carry out the entire process of peptide synthesis in one pot using these reagents.

A rather different approach to peptide bond formation and amide synthesis in general is to treat a mixture of a carboxylic acid and an amine with an isocyanide (2-Morpholinoethyl Isocyanide is especially suitable), which effectively acts as a dehydrating agent (eq 3). The procedure can result in extensive racemization of both reactants and products which may be supressed by the addition of HOSu; presumably an HOSu ester is the penultimate intermediate.12 The addition of HOSu also decreases racemization in polypeptide synthesis when Bates reagent {[(Me2N)3P+]2O (BF4-)2} is used as the coupling agent.13

A rather unusual coupling reaction between HOSu and glyoxylic acid tosylhydrazone leads to succinimidyl diazoacetate (eq 4); again, the leaving ability of the HOSu residue renders this a useful compound for effecting the direct transfer of a diazoacetyl function to amines, phenols, and peptides.14

Modified Barton-McCombie intermediates are best prepared from pentafluorophenyl chlorothionoformate and a catalytic quantity (15-20%) of HOSu in refluxing benzene rather than by using 4-Dimethylaminopyridine, the rather more conventional catalyst of acyl group transfer (eq 5).15

1. Anderson, G. W.; Zimmerman, J. E.; Callahan, F. M. JACS 1964, 86, 1839; Wegler, R.; Grewe, F.; Mehlhose, K. U.S. Patent 2 816 111, 1957 (CA 1958, 52, 6405i).
2. For a review, see: Klausner, Y. S.; Bodansky, M. S 1972, 453.
3. For examples, see: Wunsch, E.; Drees, F. CB 1966, 99, 110; Manesis, N. J.; Goodman, M. JOC 1987, 52, 5331; Mukaiyama, T.; Goto, K.; Matsuda, R.; Ueki, M. TL 1970, 1901; Bosshard, H. R.; Schechter, I.; Beger, A. HCA 1973, 56, 717.
4. Kemp, D. S.; Trangle, M.; Trangle, K. TL 1974, 2695.
5. For a review of side reactions in peptide synthesis, see: Martinez, J. S 1981, 333.
6. Cline, G. W.; Hanna, S. B. JOC 1988, 53, 3583.
7. Fujino, M.; Kobayashi, S.; Obayashi, M.; Fukuda, T.; Shinagawa, S.; Nishimura, O. CPB 1974, 22, 1857.
8. Terao, S.; Shiraishi, M.; Kato, K.; Ohkawa, S.; Ashida, Y.; Maki, Y. JCS(P1) 1982, 2909.
9. Ogura, H.; Kobayashi, T.; Shimizu, K.; Kawabe, K.; Takeda, K. TL 1979, 4745.
10. Ogura, H.; Nagai, S.; Takeda, K. TL 1980, 21, 1467.
11. Takeda, K.; Sawada, I.; Suzuki, A.; Ogura, H. TL 1983, 24, 4451.
12. Wackerle, L. S 1979, 197; Marquarding, D.; Aignar, H. Ger. Offen. 2 942 606, 1979 (CA 1981, 95, 62 731j).
13. Bates, A. J.; Galpin, I. J.; Hallett, A.; Hudson, D.; Kenner, G. W.; Ramage, R.; Sheppard, R. C. HCA 1975, 58, 688.
14. Ouihia, A.; Rene, L.; Guilhem, J.; Pascard, C.; Badet, B. JOC 1993, 58, 1641.
15. Barton, D. H. R.; Jaszberenyi, J. Cs. TL 1989, 30, 2619. For an application, see: Gervay, J.; Danishefsky, S. JOC 1991, 56, 548.

David W. Knight

Nottingham University, UK

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