Furthermore, the methyl group at C-15 was located at an equatorial position by the large coupling constant (11.9 Hz) between H-14a and H-15.
The relative configuration of H-7′/H-8′ was threo orientation, for the large coupling constant (J = 8.1 Hz) between H-7′ and H-8′, along with ROESY correlation of H-2′ and H-6′ with H-8′ and there was no NOE correlation between H-7′ and H-8′ [34, 35] 35] (Fig. 3).
Because of a small proton-proton coupling between H4′a and H3′ (around 3 Hz) and a large coupling between H4′b and H3′ (around 9 Hz), as shown in Table 2; Fig. S4 (Electronic supplementary material), only two out of three conformers of the C5′-C4′-C3′-O dihedral are possible main conformations.
The NOE correlations of H-11 with H-13, H3-14 and H3-15, H-5 with H-10, together witogetherarger coupling constants (3J5, 11 = 11.0 Hz) betwith H-5 and H-11 atheibuted the a-orientation for H-11 and β-orientation for H-5 and H-10 (Fig. 3).
f(2*) then denotes the fraction of molecules where the bond is conserved between the observed carbon and the neighboring carbon with the larger coupling.
f(2*) then denotes for fraction of molecules where the bond is conserved between the observed carbon and the neighbouring carbon with the larger coupling.
In most experiments, the spermathecae and seminal receptacle were removed to avoid the large mechanical coupling between spermatheca and oviduct movements (Figs. 10, 11).
Let us now investigate the limit of large coupling parameter.
The dqfCOSY spectrum of the resulting sample revealed a large vicinal diaxial coupling between H3 and the axial proton of the C4 methylene, H4a, indicating that the carboxyl group had to be equatorial in KthP-derived chloropiperazate, as was found to be the case for synthetic (3 S,5 R -chloropiperazate.
This large coupling constant is on the boundary between those of cis and trans vinyl groups and so the precise identification of this compound from the NMR data alone was not possible.[ 13] If the reaction mixture was extracted with aqueous ammonia (2 m) to remove any soluble copper species, then 3 aa, 5 aa and 6 aa were again observed along with a new product denoted 4 aa (entry 2).
