C O M M U N I C A T I O N S
Scheme 1a
pure carbobicyclic scaffolds outlined here will be of general utility
in the stereocontrolled construction both of natural products and
of drug candidates.
Acknowledgment. We thank the NIH (GM60287) for financial
support of this work, James A. Golen for the X-ray analysis, and
John Dykins for the high-resolution mass spectra. This work is
dedicated to the memory of David L. Coffen, a master of the science
of asymmetric synthesis.
a Reagents and conditions: (a) 9-BBN, THF; NaOH, H2O2 (ref 10); (b)
Pd/BaSO4, pyridine, H2; (c) NaH, TBAI, THF, BnBr, reflux; (d) O3, CH2Cl2;
PPh3; (e) N2H4, HOCH2CH2OH, 210 °C; (f) H2, Pd/C, EtOH; (g) Dess-
t
Martin reagent (ref 11), CH2Cl2; (h) nPr+PPh3Br-, BuOK, THF; (i) H2,
Supporting Information Available: Experimental details and
spectra for all new compounds (PDF, CIF). This material is available
Pd/C, EtOH.
Table 2. Construction of Cis Carbobicyclic Ring Systems
References
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a All products are single diastereomers. b Ref 12. c Starting from 2a, TsCl,
pyridine, DMAP; O3, CH2Cl2; PPh3. d Starting from 13, NaOH, PhSH;
mCPBA. e Starting from 2a, 2b, and 2c, BsCl, pyridine, DMAP; O3, CH2Cl2,
MeOH; NaBH4; MsCl, Et3N, CH2Cl2. f Starting from 2a, BsCl, pyridine,
DMAP; mCPBA, CH2Cl2; BF3‚Et2O, LiCH2SO2Ph (ref 13); Dess-Martin
reagent, CH2Cl2; HOCH2CH2OH, THF, HC(OEt)3 (ref 14).
groups are versatile and can be converted into other functional
groups. It is also possible to include other functional groups in the
ring, as shown in entry 4.
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(14) Koreeda, M.; Brown, L. J. Org. Chem. 1983, 48, 2122.
While many methods for polycarbocyclic ring construction have
been developed, only a few of these lead directly to enantiomerically
pure products. We expect that the approach to enantiomerically
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