Page 1185 - Advanced Organic Chemistry Part B - Reactions & Synthesis

12.17. Various terpene-derived materials are important in the formulation of 1161
fragrances and flavors. One example is the tricyclic furan shown below, which
PROBLEMS
®
is commercially used under the trademark Ambrox. The synthetic sequences
below have been developed to prepare related structures. Suggest reagents for
each step in these sequences.

O

Ambrox R

a. This sequence was developed to avoid the use of transition metal reagents
and minimize by-products.

O OH
OH
OH
HO HO
OH OH O O
1 2 OH 3
4
O
CH = O
O 5
O

b. The following sequence led to the 6- –hydroxy derivative.

HO HO HO O
1 2 4
O OH OH
3
OH OH O 2 CCH 3 O 2 CCH 3

OH
O O
7 5
OH
6
OH OH O 2 CCH 3

12.18. The closely related enones 18-A and 18-B give different products when treated
with Pb OAc in CH CN. Formulate mechanisms to account for both products
4 3
and identify the factor(s) that lead to the divergent structures.