I I I
CH3 I CH3 I CH3 I CH3
H-C-CH3 I H3C-C-H I H3C-C-H I H-C-CH3
CH2 I CH2 I CH2 I CH2
H-C-CH3 I H3C-C-H I H-C-CH3 I H3C-C-H
(1) (2) (3) (4)
1 si 2 = mezoforma => 1 izomer
3 si 4 = diasteroizomeri