Abstract
Solubilization of proline as the triethylammonium salt allows
N-protection (as the Boc, Cbz or Moc derivative) and subsequent
esterification or amidation of the carboxy terminus to be performed
in an efficient one-pot fashion. Based on this concept, highly practical
protocols were developed to prepare a series of proline derivatives
(including Pro-Ser dipetides, Weinreb amides and N-protected proline
esters), which are important intermediates, for instance, for the
synthesis of proline-derived peptides, chiral reagents and catalysts
for asymmetric synthesis.
Key words
proline derivatives - peptides - carbamates - N-protecting groups - solvent effects - coupling
reagents
References
1a Gentilucci L.
Cerisoli L.
De Marco R.
Tolomelli A.
Tetrahedron Lett.
2010,
51:
2576
1b Dai N.
Etzkorn FA.
J. Am. Chem. Soc.
2009,
131:
13728
1c Chiba K.
Sugihara M.
Yoshida K.
Mikami Y.
Kim S.
Tetrahedron
2009,
65:
8014
1d Heiser U, Niestroj AJ, and Schulz I. inventors; WO
Patent 007415 A2.
1e Sun H.
Martin C.
Kesselring D.
Keller R.
Moeller KD.
J.
Am. Chem. Soc.
2006,
128:
13761
1f Pfeifer ME.
Linden A.
Robinson JA.
Helv. Chim. Acta
1997,
80:
1513
1g Falorni M.
Porcheddu A.
Giacomelli G.
Tetrahedron:
Asymmetry
1996,
7:
1999
2a Woodin KS.
Jamison TF.
J.
Org. Chem.
2007,
72:
7451
2b Ni Y.
Zhao G.
Ding Y.
J.
Chem. Soc., Perkin Trans. 1
2000,
3264
2c Sibi M.
Christensen J.
J. Org. Chem.
1999,
64:
6434
2d Céliméne C.
Dhimane H.
Lhommet G.
Tetrahedron
1998,
54:
10457
3a Chena Z.
Ye T.
New J. Chem.
2006,
30:
518
3b Yokokawa F.
Sameshima H.
In Y.
Minoura K.
Ishida T.
Shioiri T.
Tetrahedron
2002,
58:
8127
4a Corey EJ.
Bakshi RK.
Shibata S.
J. Am. Chem.
Soc.
1987,
109:
5551
4b Corey EJ.
Helal CJ.
Angew.
Chem. Int. Ed.
1998,
37:
1986
4c Stemmler RT.
Synlett
2007,
997
5 Corey EJ.
Angew.
Chem. Int. Ed.
2002,
41:
1650
6a Bertelsen S.
Jørgensen KA.
Chem.
Soc. Rev.
2009,
38:
2178
6b MacMillan DWC.
Nature (London)
2008,
455:
304
6c Dondoni A.
Massi A.
Angew. Chem. Int. Ed.
2008,
47:
4638
7 Zaminer J.
Brockmann C.
Huy P.
Opitz R.
Reuter C.
Beyermann M.
Freund C.
Müller M.
Oschkinat H.
Kühne R.
Schmalz H.-G.
Angew.
Chem. Int. Ed.
2010,
49:
7111
8a Anderson GW.
McGregor AC.
J. Am. Chem. Soc.
1957,
79:
6180
8b Kaname M.
Mashige H.
Yoshifuji S.
Chem.
Pharm. Bull.
2001,
49:
531
9a Takeda K.
Akiyama A.
Nakamura H.
Takizawa Y.
Mizuno Y.
Takayanagi H.
Harigaya Y.
Synthesis
1994,
1063
9b Held I.
Von Den Hoff P.
Stephenson DS.
Zipse H.
Adv.
Synth. Catal.
2008,
350:
1891
10 Hayashi Y.
Matsuzawa M.
Yamaguchi J.
Yonehara S.
Matsumoto Y.
Shoji M.
Hashizume D.
Koshino H.
Angew. Chem. Int. Ed.
2006,
45:
4593
2 described so far lead to N -Moc (or N -Eoc)-protected
proline esters; see:
11a Kanth JVB.
Perlasamy M.
Synth.
Commun.
1995,
25:
1523
11b Oliveira DF.
Miranda PCML.
Correia Carlos RD.
J.
Org. Chem.
1999,
64:
6646
12 Protic solvents such as water or alcohols
are rival nucleophiles.
13 The esterification step requires DMAP
as a nucleophilic catalyst, which activates both Boc2 O
(to react with the carboxylate) and the resulting mixed anhydride
(to react with t -BuOH); see ref. 9a.
14 Zhou ZH.
Tang YL.
Li KY.
Liu B.
Tang CC.
Heteroat.
Chem.
2003,
14:
603
15a König W.
Geiger R.
Chem.
Ber.
1970,
103:
788
15b Deng S.
Taunton J.
Org. Lett.
2005,
7:
299
16 DCC-mediated coupling of 10 in the presence of DMAP led to the isolation
of 2e in only 48% yield, along
with 21% of the tert -butyl ester 2b resulting from the reaction of 7a with tert -butyl
alcohol.
17a Ho G.-J.
Mathre DJ.
J.
Org. Chem.
1995,
60:
2271
17b Soloshonok VA.
Ueki H.
Jiang C.
Cai C.
Hruby VJ.
Helv.
Chim. Acta
2002,
85:
3616
18 Kim S.
Lee JI.
Kim YC.
J.
Org. Chem.
1985,
50:
560
19 Methyl ester 2j was
synthesized in 93% yield with K2 CO3 instead
of Et3 N.¹¹b
20 For example, the yield of tert -butyl ester 2k (Table
[²
21 Mayr H.
Ofial AR.
Angew. Chem. Int. Ed.
2006,
45:
1844 ; and references cited therein
22 Beckett RP.
Davies SG.
Mortlock AA.
Tetrahedron: Asymmetry
1992,
3:
123
23 Gibson FS.
Bergmeier SC.
Rapoport H.
J.
Org. Chem.
1994,
59:
3216
24 Anderson GW.
Callahan FM.
J. Am. Chem. Soc.
1960,
82:
3359
25 Irie K.
Ishida A.
Nakamura T.
Oh-ishi T.
Chem. Pharm. Bull.
1984,
32:
2126
