Development of a Facile Tandem Asymmetric Epoxidation/Ring-opening Protocol: An Efficient Entry to Enantiomerically Enriched Tertiary Naphthtoquinols Dora Carrico-Moniz, Department of Chemistry, Wellesley College, Wellesley, MA 02481
The tertiary naphthoquinol C4’ is a key structural component of the architecturally interesting spiroxin family of natural products.
Br O
Zn Valproic Acid Pd[(R)-binap]Cl2 88% Yield 90% ee (95:5 er)
1
OH
(S)-5
2) Br2, Et3N 3) DBU, 71% Yield, 2 steps
(S)-2
4 (MeCN)2PdCl2 AsPh3 57% Yield
OTBDPS (S)-3
O
TBAF 85% Yield OTBDPS
Sn
1) TBDPS-Cl, 76% Yield
mCPBA
OH
OH
(S)-6
(S)-7
OH
(COCl)2, DMSO DIPEA 76% from (S)-6 83% ee (91.5:8.5 er)
O (S)-8
We have developed an efficient catalytic asymmetric approach to the tertiary naphthoquinol stereogenic center present in the spiroxin framework, via tandem oxidation/ring opening of a cyclic 3,4epoxyalcohol. This new route allows a facile entry into relatively inaccessible tertiary naphthoquinols with high enantioselectivity and without the need of chiral auxiliaries.
