Table 1 ¹H-NMR (400 MHz) data of lignans 1–4 from the flowers of Forsythia koreana (δ in ppm, coupling pattern, J in Hz)

1

2

6.54, d, 1.6

6.71, br. s

6.38, d, 1.6

6.53, d, 1.6

3

4

5

6.77, d, 8.4

7.04, d, 8.2

6.80, d, 8.4

6.67, d, 8.4

6

6.56, dd, 8.4, 1.6

6.53, br. d, 8.2

6.49, dd, 8.4, 1.6

6.48, dd, 8.4, 1.6

7

2.47, overlapped

2.47, overlapped

2.52, overlapped

2.49, overlapped

8

2.45, m

2.61, m

2.45, m

2.44, m

9a

4.10, dd, 8.8, 6.0

4.11, dd, 8.9, 6.3

4.13, dd, 8.8, 6.5

4.13, dd, 8.8, 6.0

9b

3.98, dd, 8.8, 8.4

3.85, dd, 8.9, 8.4

3.85, dd, 8.8, 8.7

3.88, dd, 8.8, 8.3

1′

2′

6.65, d, 2.0

6.55, br. s

6.59, d, 2.0

6.71, br. s

3′

4′

5′

6.69, d, 8.0

6.78, d, 8.7

6.81, d, 8.0

7.01, d, 8.0

6′

6.57, dd, 8.0, 2.0

6.52, br. d, 8.7

6.57, dd, 8.0, 2.0

6.64, br. d, 8.0

7′a

2.83, dd, 14.0, 5.2

2.87, dd, 14.8, 5.5

2.91, dd, 14.0, 5.2

2.85, dd, 14.0, 5.2

7′b

2.77, dd, 14.0, 7.2

2.74, dd, 14.8, 7.6

2.86, dd, 14.0, 7.2

2.80, dd, 14.0, 7.2

8′

2.59, m

2.42, m

2.59, m

2.63, m

9′

1″

4.85, d, 7.8

4.85, d, 7.8

2″

3.57, overlapped

3.50, overlapped

3″

3.56, overlapped

3.49, overlapped

4″

3.99, overlapped

3.37, overlapped

5″

3.72, overlapped

3.37, overlapped

6″a

3.75, dd, 11.6, 4.4

3.86, dd, 11.6, 4.4

6″b

3.66, dd, 11.6, 1.2

3.64, dd, 11.6, 1.2

OMe

3.73, s

3.74, s

3.78, s

3.77, s

OMe

3.73, s

3.73, s

3.77, s

3.74, s

OMe

3.73, s

3.70, s