PROGRESS OF STUDIES ON THE NATURAL CEMBRANOIDS FROM THE SOFT CORAL SPECIES OF SARCOPHYTON GENUS - Medicinal Chemistry of Bioactive Natural Products - page 294

H

a

H

b

C HO

SnBu 3

SnBu 3 SnBu 3

278 279 274

OH OMOM OH OH OH

OH

c d e f

280 281 282

OAc O O

O O

CO 2 H

g

h

283 272 256
Reagents and Conditions: (a) (R)-( þ )-BINOL-H, then MOMCl, i Pr 2 NEt; (b) i. LDA, CH 2 O; ii.
BuOMgBr, (CH 2 ) 5 CON ¼ NCO(CH 2 ) 5 ; (c) BF 3 Et 2 O, CH 2 Cl 2 , 78 C, 88%; (d) i. 10% HCl, THF; ii.
NaBH 4 , EtOH, 72%; (e) i. Red-Al, THF, I 2 , THF; ii. LiCuMe 2 , THF, 65%; (f) i. TBSCl, Et 3 N, CH 2 Cl 2 ; ii.
AcCl, Py, 0 C; iii. TBAF, HOAc, THF; iv. PDC, DMF, 52%; (g) i. K 2 CO 3 , MeOH; ii. DCC, DMAP,
CH 2 Cl 2 ; (h) i. LDA, CH 2 O (g), THF, 78 C; ii. MsCl, Py; 3) DBU, benene, reflux.

Scheme 6-38

Ph MeO 2 C

O N 2

N N

a b c

d

N N

OBn

O O

OBn OBn

O

Ph

Ph

OBn

286

OH

285

284

287 288

MeO 2 C MeO 2 C

OBn OBn

O

O

OBn

OBn

g

f

O O

Br

+

SO 2 Ph

SO 2 Ph

e

289 290 291

292

HO

O O O

O

j

O

h i

293 294 295
Reagents and Conditions: (a) LHMDS, then epoxide 286; (b) i. NaH, farnesyl bromide; ii. aq HCl, THF,
74%; (c) NaH, (MeO) 2 CO, DBU, PNBSA, 63%; (d) Rh(Oct) 2 , 90%; (e) NaOMe, 88%; (f) i. LiAlH 4 ,
84%; ii. TsCl, Et 3 N; 3) NaSO 2 Ph, Bu 4 NI, DMF, 84%; (g) i. SeO 2 , t-BuOOH; ii. CBr 4 ,Ph 3 P, 50%; (h) i.
LDA, THF; ii. Na/NH 3 , 61%; (i) PDC, Ac 2 O, 58%; ( j) i. CH(OMe)(NMe 2 ) 2 ; ii. DIBAL-H, 64%.

Scheme 6-39

294