Advices For Studying Organic Chemistry

ii) Protonation of (3S)-2,3-oxidosqualene by squalene oxidocyclase gives the

oxygen a formal positive charge and converts it to a good leaving group.

O

CH 3

CH 3

CH 3

CH 3

H 3 C H 3 C

CH 3

Enz−H CH^3

3 2 7

6 11

(^101514)
19
18
Squalene
(3S)-2,3-Oxidosqualene
CH 3
H 3 C
CH 3
Protosteryl cationCH^3 H
H 3 C
CH 3
CH 3
HO H
H
CH (^319)
(^10151418)
6 11
7

• Oxidocyclase
  iii protonated epoxide makes the tertiary carbon (C2) electron deficient
  (resembling a 3° carbocation), and C2 serves as the electrophile for an addition
  4 nce of 1,2-Methanide and
  1,2-Hydride Rearrangements

1. The subsequent transformations involved a series of migrations (carbocation
   i) The process begins with a 1,2-hydride shift from C17 to C18, leading to
   ii) The developing positive charge at C17 facilitates another hydride shift from
   hyl shift from C14 to C13 and C8 to
   ) The
   with the double bond between C6 and C7 in the squalene chain ⇒ another 3°
   carbocation begins to develop at C6.
   iv) The C6 carbocation is attacked by the next double bond, and so on for two
   more alkene additions until the exocyclic tertiary proteosteryl cation results.

. An Elimination Reaction Involving a Seque

rearrangements) followed by removal of a proton to form an alkene.

development of positive charge at C17.

C13 to C17 which is accompanied by met

C14.