Efficient electrochemical deprotection of carboxylic and amino acids from their 2-(hydroxymethyl)-1,3-dithiane (dim) esters

Organic Letters

Volumn 2, Issue 6, 2000, Pages 799-801

  Barnhurst, Loren A ^a   Wan, Yongqin ^a   Kutateladze, Andrei G ^a  

^a UNIVERSITY OF DENVER   (United States)

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Indexed keywords

EID: 0001753313     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol005537w     Document Type: Article

References (10)

1. For a review see: Gröbel, B.-T.; Seebach, D. Synthesis 1977, 357.
2. McHale, W. A.; Kutateladze, A. G. J. Org. Chem. 1998, 63, 9924.
3. 2 Pt cathode and anode, 20°C, acetonitrile, 9 mM Dim ester, 0.1 M LiClO4, under constant current (3 mA) conditions. Workup included evaporation of the solvent, addition of 10% aqueous KOH, ether extraction of organic side products, and acidification with hydrochloric acid followed by ethereal extraction of the acid.
4. Nicholas, A. M. d. P.; Arnold, D. R. Can. J. Chem. 1982, 60, 2165.
5. Glass, R. S.; Petsom, A.; Wilson, G. S. J. Org. Chem. 1986, 51, 4337.
6. Kunz, H.; Waldmann, H. Angew. Chem., Int. Ed. Engl. 1983, 22, 62. Waldmann, H.; Kunz, H. J. Org. Chem. 1988, 53, 4172.
7. Kunz, H.; Waldmann, H. Angew. Chem., Int. Ed. Engl. 1983, 22, 62. Waldmann, H.; Kunz, H. J. Org. Chem. 1988, 53, 4172.
8. General procedure for esterification with DCC/4-aminopyridines: Hassner, A.; Alexanian, V. Tetrahedron Lett. 1978, 46, 4475-4478.
9. 6 reported that in acidic media the Dim esters were stable enough to allow selective deprotection of the t-BOC-protected N-termini. We also tested the stability of Dim esters under basic conditions. For example, an ethereal solution of 3 was shaken vigorously with 10% KOH. The layers were separated. The organic layer contained pure starting material. The aqueous layer was acidified with HCl and extracted with ether. No benzoic acid was detected, attesting to the stability of Dim esters to bases.
10. 4. Ether was removed to give 41 mg (74%) of faintly yellow oil. Both NMR and HPLC confirmed pure N-t-BOC-Phe-OH.