中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | 5-hydroxy-1-methoxy-4-naphthalenecarboxaldehyde | 67243-03-2 | C12H10O3 | 202.21 |
4,8-二甲氧基-萘-1-甲醛 | 4,8-dimethoxy-1-naphthaldehyde | 69833-11-0 | C13H12O3 | 216.236 |
中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | 7-bromo-4,8-dimethoxynaphthalene-1-carbaldehyde | 195504-97-3 | C13H11BrO3 | 295.133 |
—— | 8-benzyloxy-7-bromo-4-methoxynaphtalene-1-carbaldehyde | 222728-70-3 | C19H15BrO3 | 371.23 |
2-乙酰基-7-溴-4,8-二甲氧基-1-萘酚 | 2-acetyl-7-bromo-4,8-dimethoxy-1-naphthol | 195505-00-1 | C14H13BrO4 | 325.159 |
—— | 7-bromo-4,8-dimethoxy-1-naphthol | 195504-98-4 | C12H11BrO3 | 283.122 |
The preparation of oxygenated naphthyl stannanes bearing an ortho-methoxy substituent is described, including stannanes (23) and (25) which are key intermediates for the synthesis of dimeric pyranonaphthoquinone antibiotics. Stannanes (17), (19) and (21)–(23) were obtained by metal–halogen exchange of the corresponding bromonaphthalenes. In an alternative approach to effect stannylation, a palladium(0)-mediated coupling reaction using hexaalkylditin reagents was examined. The Stille coupling reaction between naphthyl stannanes (23) and (25) and the corresponding bromonaphthalenes (11) and (24) failed to effect coupling to the desired binaphthyls.
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–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).