PROGRESS OF STUDIES ON THE NATURAL CEMBRANOIDS FROM THE SOFT CORAL SPECIES OF SARCOPHYTON GENUS - Medicinal Chemistry of Bioactive Natural Products - page 277

SO 2 Ph

THPO

SO 2 Ph

THPO

172 a

S

Cl

+

S

S

S

173 174

O

b c

O

±

175 59
Reagents and Conditions: (a) 50% NaOH/TBAB, rt, 20 h; (b) i. PPTs/MeOH, ii. Na(Hg), Na 2 HPO 4 ,
MeOH; iii. HgCl 2 , CaCO 3 ; iv. PCC, CH 2 Cl 2 ; (c) TiCl 3 /AlCl 3 , Zn-Cu, DME, 36 h.

Scheme 6-16

An alternative strategy for preparing cembrene C (27) by this group is described
below. The dicarbonyl precursor keto enal 176 was prepared from geraniol

(Scheme 6-19). 98

6.4.3 Total Synthesis of Several Natural Epoxy Cembrenoids

Naturally occurring cembranoid epoxides (cembranoxides) (Figure 6-10) have been
found as chemical components of various tropical marine soft corals and represent a

O

OH

O

a

O

+

a

b

Cembrene C ( 27 )

176 91

b

O

O

geraniol

+

Y

X

X = Cl, Br, I
Y = SPh, SO 2 Ph

Scheme 6-17