Table S1.

¹H and ¹³C NMR chemical shifts (δ, parts per million) for the carbohydrate moiety of the product generated by WbbB^540-1106 using acceptor A

Sugar residue	Residue	C-1, H-1	C-2, H-2	C-3, H-3	C-4, H-4	C-5, H-5	C-6, H-6 (6a, 6b)
→3)-β-d-GlcpNAc-(1→*	A	102.3, 4.81	57.0, 3.78	82.8, 3.61	69.7, 3.50	77.0, 3.43	61.9, 3.75, 3.92
→4)-α-l-Rhap-(1→†	B	102.4, 4.85	72.1, 3.74	71.6, 3.82	81.4, 3.60	68.5, 4.00	18.2, 1.27
→3)-β-d-GlcpNAc-(1→	A′	101.7, 4.46	56.8, 3.71	82.8, 3.56	69.7, 3.43	77.1, 3.39	62.0, 3.70, 3.87
β-d-GlcpNAc-(1→	A′′	102.7, 4.77	57.1, 3.68	75.2, 3.56	71.3, 3.46	77.0, 3.43	61.9, 3.75, 3.92

Residues marked with a prime belong to the reducing-end repeat unit, and a residue marked with double primes is a terminal nonreducing residue.

^*Chemical shifts for NAc groups are at δ_H 2.03‒2.07, δ_C 23.6 (CH₃) and 175.0‒175.8 (CO).

^†Rha B′ H-1 is at δ_H 4.82.