Table 1. NMR Data for Leptochelin A (1) (CDCl₃, 400 MHz)^a.

Position	δC, mult	δH, mult	HMBC	ROESY
1	178.9, C
2	85.4, C
3a	41.8, CH2	3.43, d (11.7 Hz)	2, 4, 13	3b, 13
3b		3.58, d (11.7 Hz)	1, 2, 13	3a
4	176.8, C
5	61.5, C
6	64.4, CH	3.68, d (7.8 Hz)	7, 8	14
7	75.4, CH	3.93, ovlp	6, 9	8a, 8b, 16
8a	37.8, CH2	3.72, ovlp	6, 7	7
8b		3.88, ovlp	6, 7, 9	7
9	186.5, C
10	62.7, C
NH2-10		not observed
11	77.9, CH	3.83, bs		12, 15, 16
12	50.2, CH	4.51, ovlp		11, 16, NH-12
NH-12		10.08, d (7.7 Hz)		12, 16, 19a, 18 wk
13	22.9, CH3	1.46, s	1, 2, 3	3a, 27
14	21.1, CH3	1.57, s	4, 5, 6	ovlp
15	31.1, CH3	1.53, s	9, 10, 11	ovlp
16	15.4, CH3	1.14, d (7.4 Hz)	11, 12	7, 11, 12, NH-12
17	175.2, C
18	57.8, CH	4.40, ovlp		19a, 19b, 21/25
NH-18		8.06, d (7.0 Hz)		18, 19a, 21/25, 27, NH-18, 28b wk, 19b wk
19a	37.1, CH2	2.91, dd (14.3, 11.5 Hz)	17, 18, 20, 21/25	21/25, NH-18
19b		3.24, dd (14.3, 4.1 Hz)	18, 20, 21/25	18, 21/25
20	135.7, C
21/25	130.9, CH	7.22, d (8.3 Hz)	19, 22/24, 23	18, 19a, 19b, 22/24,
22/24	131.9, CH	7.46, d (8.3 Hz)	20, 21/25,23	21/25
23	121.0, C
26	173.0, C
27	67.4, CH	4.57, ovlp		13, 28a, 28b, NH-18
28a	69.4, CH2	4.33, t (7.8 Hz)	26, 27, 29	27
28b		4.45, ovlp	26, 27, 29	13 wk
29	171.0, C
30	118.0, C
31	165.0, C
32	111.2, C
33	137.5, CH	7.58, dd (7.9, 1.8 Hz)	30, 31, 35	34
34	112.8, CH	6.29, t (7.9 Hz)	30, 32	33, 35
35	130.2, CH	7.61, dd (7.9, 1.8 Hz)	29, 33	34

^aROESY spectrum was obtained in CDCl₃ on a 500 MHz instrument. Note: “ovlp” denotes signal overlap and “wk” indicates a weak but notable correlation. ¹⁵N NMR shifts from a ¹H–¹⁵N gHMBC experiment (500 MHz, CDCl₃) (SI Appendix, Figure S13): δ_N 285.8 (N-2), 122.5 (NH-18), 119.5 (NH-12), 37.9 (NH₂-10). N-27 not observed.