(2) Cram Rule:1b If chelation cannot occur, 6 was
proposed to be the preferred reactive conformation
based on steric reasons (Scheme 3): the decisive
steric interaction to be avoided was thought to be
between the large substituent L and the carbonyl
group. Consequently, L is oriented anti to the carbonyl
group, placing S and M on different sides of
the carbonyl group. A nucleophile will now preferentially
attack from the side of the small substituent
S, leading to 7 as the major product, the so-called
Cram or Felkin-Anh product.6