Conformational analysis of natural products

Hydroxymethyl conformation from coupling constants - monosaccharides

The experimental values of the 3JH5,H6 [1] are interpreted using two different sets of limiting values.
The values of Bock and Duus [1] are based on the Karplus equation of Haasnoot et al. [2] whereas those of Stenutz et al. [3] are based on quantum mechanical calculations in 2-hydroxymethyl tetrahydropyran (oxane). Apart from slight differences in the relationship between torsion angles and coupling constants Stenutz et al. assume a larger torsion (65°) for the gg and gt rotamers.
The θ torsion is defined here as C5-C6-O6-X, i.e. H or glycosyl/alkyl. The amount of trans can be estimated from 2JH6R,H6S if the amounts of the ω rotamers are known.
The ω rotamers are estimated to be accurate to about +-5%, but the error in θ is larger since 1) the relationship between 2JH6R,H6S is less reliable and 2) the ω rotamer populations are required. An error of at least +-10% is to be expected.
[1] K. Bock and J.Ø. Duus, J. Carbohydr. Chem. 13 (1994) 513-543
[2] C.A.G. Haasnoot, F.A.A.M. DeLeeuw and C. Altona, Tetrahedron 36 (1980) 2783-2792.
[3] R. Stenutz, I. Carmichael, G. Widmalm and A.S. Serianni, J. Org. Chem. 67 (2002) 949-958 DOI 10.1021/jo010985i
Hydroxymethyl coupling constants and rotamer distribution in hexopyranoses
Coupling constants Bock & Duus Stenutz et al.
Compound 3JH5,H6R 3JH5,H6S 2JH6R,H6S Pgt Pgg Ptg Pgt Pgg Ptg θtrans
methyl α-D-glucopyranoside [97-30-3]5.492.39-12.35 5057-7 474210 7
methyl α-D-glucopyranoside (CD3OD) [97-30-3]5.642.40-11.80 5156-7 494111 26
methyl β-D-glucopyranoside [7000-27-3]6.112.47-12.31 5650-6 543511 9
α-D-glucopyranose (DMSO) [9050-36-6]5.002.30-11.20 4563-8 424810 46
β-D-glucopyranose [921-60-8]5.782.29-12.33 5355-8 51409 9
β-D-glucopyranose (DMSO) [921-60-8]5.902.20-11.80 5555-10 53398 27
methyl α-D-mannopyranoside 6.402.44-12.20 5948-7 573211 12
methyl 2-acetamido-2-deoxy-β-D-glucopyranoside 5.382.35-12.20 4959-8 464410 13
6-O-methyl-α-D-glucopyranose 5.732.37-11.04 5255-7 504010 51
6-O-methyl-β-D-glucopyranose 6.102.16-11.20 5753-10 55378 47
4,6-di-O-methyl-β-D-glucopyranose 5.641.96-11.14 5459-13 51436 50
methyl 6-O-acetyl-β-D-glucopyranoside 4.902.30-12.30 4464-8 414910 9
methyl 4,6-di-O-acetyl-β-D-glucopyranoside 3.802.10-12.60 3476-10 30628 0
methyl 6-O-phosphono-α-D-glucopyranoside (pH 1.3) 4.602.40-11.60 4166-7 375211 32
methyl 6-O-phosphonato-α-D-glucopyranoside (pH 9.3) 3.531.91-12.13 3280-12 28676 17
methyl 4-deoxy-α-D-xylo-hexopyranoside 6.203.03-12.06 54451 523117 14
methyl 4-deoxy-β-D-xylo-hexopyranoside 7.423.34-12.04 65314 651520 14
methyl 4-O-acetyl-β-D-glucopyranoside 5.902.20-12.30 5555-10 53398 10
methyl 4,4-di-hydroxy-α-D-xylo-hexopyranoside 8.402.40-12.00 8028-8 791110 19
methyl 4-thio-α-D-glucopyranoside 5.002.00-12.50 4765-12 44506 4
methyl 4-ammonio-4-deoxy-α-D-glucopyranoside (pH 2.0) 4.643.70-12.44 345610 324325 -1
methyl 4-amino-4-deoxy-α-D-glucopyranoside (pH 9.0) 5.402.46-12.42 4858-6 464311 5
C-propyl β-D-glucopyranoside 8.502.40 8127-8 811010
methyl α-D-galactopyranoside 8.603.70-11.70 75169 76024 24
methyl β-D-galactopyranoside [1824-94-8]7.504.83-11.76 581924 59536 17
β-D-galactopyranose 7.924.28-11.50 651916 66430 28