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. Author manuscript; available in PMC: 2010 Apr 13.
Published in final edited form as: Angew Chem Int Ed Engl. 2009;48(23):4158–4161. doi: 10.1002/anie.200900480

Table 1.

Examination of catalysts for selective synthesis of 8a and 9a.

graphic file with name nihms-192837-f0008.jpg
Entry Catalyst Sequence L,D-Adduct:L,L-Adduct
1 4,4-Dimethylaminopyridine (DMAP) 3:1
2 N-Methylimidazole (NMI) 4:1
3 Boc-Pmh-OMe 3:1
4 5: Boc-Pmh-Asn(trt)-His(tBu)-Asp(OtBu)-Ala-OMe 1:1.25
5 4: Boc-Pmh-Hyp(tBu)-Sp5-Tyr(tBu)-Phe-OMe 3.6:1
6 10: Boc-D-Pmh-Pro-Aib-Trp(Boc)-Phe-OMe 13:1
7 11: Boc-Pmh-D-Pro-Aib-D-Phe-D-Phe-OMe 1:2.5