Table 1. Yields of Suzuki–Miyaura cross-coupled RNA ON products obtained by post-transcriptional chemical modification of IU-labeled RNA ON transcripts^a.

Entry	RNA ON	Boronate ester substrate	Reaction time (h)	Cross-coupled product	ϵ260M−1cm−1b	Isolated yield (nmol) (with ligand L1)	Isolated yield (%) (with ligand L1)	Isolated yield (%) (with ligand L2)
1	4	9	12	9a	84 740	1.4	28	11
2	4	10	6	10a	84 740	1.5	30	24
3	4	11	6	11a	84 740	1.4	28	23
4	4	12	6	12a	92 420	1.8	36
5	4	13	6	13a	90 340	1.5	30
6	4	14	6	14a	98 553	1.6	32
7	4	15	6	15a	92 420	2.5	50	25
8	4	16	6	16′ (16a″) c	85 020	3.1 (0.9)	62 + 18 = 80	46
9	4	17	6	17a′ (17a″) c	85 400	2.6 (0.5)	52 + 10 = 62	43
10	19	17	12	19a′ (19a″) c	79 400	0.9 (0.6)	18 + 12 = 30
11	20	17	6	20a′ (20a″) c	91 800	1.8 (0.8)	36 + 16 = 52

^aAll reactions were performed on a 5 nmole scale of IU-labeled RNA transcripts. Yields reported are with respect to the RNA products isolated after HPLC purification. Concentration and yield of the product was calculated using the molar absorption coefficient (ϵ₂₆₀) of the RNA product. See Supplementary Figures S3, 4 and 6, and Table S1 for mass spectra and data.

^b ϵ₂₆₀ of coupled RNA ON products was determined by using OligoAnalyzer 3.1. In case of 9a−11a, ϵ₂₆₀of 5-vinyluridine (28) was used in place of uridine. For 12a−15a, ϵ₂₆₀ of corresponding 5-heterocycle-coupled uridine was used in place of uridine (76–78). For coupled RNA ON products using boronic esters 16 and 17, ϵ₂₆₀of 5-(benzothiophen-2-yl)vinyl uridine (3820 M⁻¹cm⁻¹) and 5-(benzofuran-2-yl)vinyl uridine (4200 M⁻¹cm⁻¹) was determined, and used in place of uridine.

^c 16a′, 17a′, 19a′ and 20a′ represent the trans isomer of cross-coupled product (major). 16a″, 17a″, 19a″ and 20a″ given in parenthesis represent the ‘cis’ isomer of cross-coupled product (minor). Isolated yields in nmoles and percentage for trans and ‘cis’ isomers products are also given.