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. Author manuscript; available in PMC: 2013 Dec 21.
Published in final edited form as: Org Lett. 2012 Dec 4;14(24):6162–6165. doi: 10.1021/ol302850n

Table 1.

N-terminal coupling of IP scaffold 2a.

graphic file with name nihms-426728-f0004.jpg
entry conditionsa yieldb
1 1.2 equiv Z-Leu-OH, 1.2 equiv HBTU, HOBt, NEt3, MeCN trace
2 1.2 equiv Z-Leu-OH, 1.2 equiv PyBOP, NEt3, DMF trace
3 1.2 equiv Z-Leu-OH, 1.2 equiv EDC, HOBt, NEt3, DCM trace
4 1.2 equiv Z-Leu-OH, 1.2 equiv EDC, 0.2 eq. DMAP, DCM 33c
5 2.0 equiv Z-Leu-OH, 2.0 equiv EDC, 0.2 eq. DMAP, DCM 58c
6 1.2 equiv Z-Leu-OH, 1.2 equiv EDC, DCM 59
7 2.0 equiv Z-Leu-OH, 2.0 equiv EDC, DCM 91
8 2.0 equiv Z-Leu-OH, 2.0 equiv PyBOP, DCM 33
9 2.0 equiv Z-Leu-OH, 2.0 equiv COMU, DCM 44
10 2.0 equiv Z-Leu-OH, 2.0 equiv DEPBT, DCM 26
11 2.0 equiv Z-Leu-OH, 2.0 equiv DCC, DCM 77
a

All reactions carried out for 24 h at rt.

b

Isolated yields.

c

HPLC analysis of a phenylalanyl derivitive showed significant epimerization of the Leu chiral center.