... of great interest in organic synthesis in general and in natural product, heterocyclic, and medicinal chemistry in par ... Chemical shifts are expressed in ppm downfield relative to tetramethykikdne as an internal standard. ... s, 6H, OCH,), 2.71 (d, Jvlc = 6.5 Hz, 2H, 2-H), 2.42 (t, J,,, =7 Hz ...