Table 1. Synthesis of norbornapeptides (Scheme 1).

No.	Sequence a	mg	Yield b (%)	[M + H]+ calc./obs. c
1	l 1 Gk 2 fPE 1 a 2	34.9	82	725.40/725.40
2	l1Gk2fPE1A2	25.9	60	725.40/725.40
3	l1Gk2FPE1a2	11.4	56	725.40/725.40
4	L 1Gk2fPE1a2	35.2	56	725.40/725.40
5	l1Gk2FPE1A2	8.6	59	725.40/725.40
6	L 1Gk2fPE1A2	22.4	61	725.40/725.40
7	L 1Gk2FPE1a2	17.5	36	725.40/725.40
8	L 1Gk2FPE1A2	34.3	81	725.40/725.40
9	L 1GK2FPE1A2	6.6	27	725.40/725.40
10	l1Gk2yPE1a2	8.9	4*	741.39/741.39
11	l1Gk2yPE1A2	10.9	59	741.39/741.42
12	l1Gk2YPE1a2	4.7	37	741.39/741.42
13	L 1Gk2yPE1a2	21.8	73	741.39/741.40
14	l1Gk2YPE1A2	7.0	49	741.39/741.43
15	L 1Gk2yPE1A2	20.5	42	741.39/741.39
16	L 1Gk2YPE1a2	18.1	72	741.39/741.41
17	L 1Gk2YPE1A2	7.3	15	741.39/741.45
18	L 1GK2YPE1A2	13.8	37	741.39/741.40
19	k 1Gk2fPE1a2	7.6	3*	740.41/740.41
20	l1Sk2fPE1a2	23.4	10*	755.41/755.41
21	l1Gk2fKE1a2	7.7	3*	756.44/756.44
22	k 1Gk2ePE1c2	7.4	3*	754.36/754.36
23	K 1Gk2fPE1A2	15.0	15*	740.41/740.41
24	L 1 S k 2fPE1A2	12.2	6*	755.41/755.41
25	L 1Gk2fKE1A2	12.0	5*	756.44/756.44
26	K 1Gk2ePE1C2	5.3	3*	754.36/754.36

^aOne-letter code for amino acids, upper case = l-, lower case = d-amino acids, sequences are given as prepared by SPPS written from N- to C-terminus, superscript numbers indicate residues involved in amide bond ring closures in 1^st (¹) and 2^nd (²) cyclization.

^bYields of HPLC purified products are given for the second cyclization reaction; asterisks mark total yields (SPPS and second cyclization). In all cases, yields are calculated for the corresponding trifluoroacetate salts.

^cESI-MS spectra (positive mode) were recorded on a LTQ OrbitrapXL hybrid ion trap-Orbitrap mass spectrometer.