“…The multiplicities of the peaks in the case of 11 are nearly identical, but the following changes in chemical shifts are to be noted: 3.92, 3.76, 5.90, 2.06, and 2.60, respectively. In view of these data, the syn-vinyl proton in 10 is seen to be deshielded by 0.92 ppm relative to the same substituent in 11. Similarly, the synmethyl group of 9 is deshielded by 0.31 ppm when compared to the same group in its anti counterpart (11).…”