. Author manuscript; available in PMC: 2020 Jul 21.

Published in final edited form as: Org Biomol Chem. 2019 Jun 24;17(27):6687–6698. doi: 10.1039/c9ob01139k

Table 1.

Average ¹³C NMR chemical shifts (δ, ppm) of C3, C1, C=O, and C1’ (CDCl₃) in the trans- and cis-Pictet-Spengler adducts (7a-7ae and 8a-8ae, respectively), and average relative shifts of the trans-adducts (Δδ_7–8, ppm).

	δ(7a-ae)	δ(8a-ae)	Δδ_7–8^a
C3	52.5 ± 0.6	56.8 ± 0.2	−4.1 ± 0.6
C1	51.7 ± 3.2	54.6 ± 3.4	−2.9 ± 0.5
C=O	174.0 ± 0.4	173.3 ± 0.2	+0.8 ± 0.2
Aryl C1’^b	134.2 ± 7.8	133.4 ± 8.2	+0.9 ± 0.5
Alkyl C1’^c	41.4 ± 4.7	40.7 ± 5.2	+0.7 ± 0.4

Defined at each of the carbons as δ for 7 – δ for 8.

Data from 16 1-aryl Pictet-Spengler analogs for which C1’ was unambiguously assigned.

Data from 7aa-ae and 8aa-ae.