
TY  - JOUR
A1  - Brimble, Margaret A. 
A1  - Nairn, Michael R. 
A1  - Prabaharan, Hishani 
A1  - Walters, Nathan B. 
T1  - Synthesis of 8-Bromokalafungin as an Intermediate for the Preparation of <emph type="2">C</emph>-Glycoside Derivatives
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1997
VL  - 50
IS  - 7
SP  - 711
EP  - 718
KW  - 
UR  - https://doi.org/10.1071/C97018 
N2  - The preparation of 8-bromokalafungin (20) which is a key intermediate for the synthesis of C-glycoside containing pyranonaphthoquinone antibiotics related to medermycin (6) is described. Although attempts to selectively monobrominate kalafungin (1) at C8 were unsuccessful, 8,10-dibromokalafungin (21) was prepared by using excess N-bromosuccinimide in chloroform. Selective bromination at C6 on a naphthalene ring was achieved upon treatment of naphthol (9) with N-bromosuccinimide (1 equiv.). Conversion of naphthol (9) into naphthoquinone (15) was effected by methylation, Baeyer&#8211;Villiger oxidation, acetylation via a Fries rearrangement and oxidation with ceric ammonium nitrate. Conversion of the 7-bromo quinone (15) into 8-bromokalafungin (20) proceeded through subsequent addition of 2-trimethylsilyloxyfuran (16) followed by oxidative rearrangement of the resultant furonaphthofuran (17) to furonaphthopyran (18). After reduction of the lactol (18) to cis ether (19), demethylation and epimerization at C5 with boron tribromide afforded 8-bromokalafungin (20). 8-Bromokalafungin (20) failed to undergo Pd(0)-mediated cross-coupling reactions with the stannyl glucal (22). 
ER  -

