Ch

can be easily resolved: CH3 (h13) must be connected to c17 (Cq) since this is the only sp3-hybridized quaternary carbon correlated to h13. If CH3 (h13) were connected to c28 or c29 it could only show three HMBC correlations since c28 and c29 are sp2-hybridized and can only be bonded to two carbons in addition to CH3 (h13). Likewise, CH3 (h10) must be bonded to c16 for the same reasons (Fig. 11.59). In this fragment, we can add a methyl ester since h20 (CH3) shows an HMBC correlation to c30, which has a chemical shift (178.8 ppm) consistent with an ester carbonyl group.

11.10.5 2D COSY Spectrum

Figure 11.60 shows a portion of the DQF-COSY spectrum of LGJC3 with part of the HSQC spectrum aligned above it and, turned sideways, to the left side. There are correlations from h18 (1.56 ppm) to h8b (1.70 ppm, strong) and h8a (2.42 ppm, weak). Since these cannot be geminal couplings, we can assume that c8 is attached to c18 and the relationship is vicinal (three bonds) between h18 and h8b and between h18 and h8a. We can now connect the h1/h2 fragment to the h10 fragment (Fig. 11.61). Likewise, the h6a COSY crosspeak to h12a (Fig. 11.60) allows us to connect the h9 fragment to the h10 fragment. Because of the shared HMBC correlations from h1 (CH3) and h9 (CH3) to

Figure 11.60 shows a portion of the DQF-COSY spectrum of LGJC3 with part of the HSQC spectrum aligned above it and, turned sideways, to the left side. There are correlations from h18 (1.56 ppm) to h8b (1.70 ppm, strong) and h8a (2.42 ppm, weak). Since these cannot be geminal couplings, we can assume that c8 is attached to c18 and the relationship is vicinal (three bonds) between h18 and h8b and between h18 and h8a. We can now connect the h1/h2 fragment to the h10 fragment (Fig. 11.61). Likewise, the h6a COSY crosspeak to h12a (Fig. 11.60) allows us to connect the h9 fragment to the h10 fragment. Because of the shared HMBC correlations from h1 (CH3) and h9 (CH3) to

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