Methane → HCID 13036884, compound

Participants

Reaction Steps

A solution of t-butyl (6R,7R and S[5:1])-3-acetoxymethyl-7-azido-7-bromoceph-3-em-4-carboxylate (17.255 g, 39.8 mmole), pyridine (3.24 ml, 40 mmole), silver tetrafluoroborate (8.55 g, 43.8 mmole) in methylene chloride (160 ml), and methanol (320 ml) was stirred at +20° to +25° for 16 hours (a grey precipitate appeared within 1 to 2 minutes, but t.l.c. indicated that the long reaction-time was necessary). The mixture was filtered through Celite and the filtrate was evaporated and chromatographed on silica gel (250 g) in 5% ethyl acetate in benzene. A mixture of t-butyl (6R,7R and S[1:5])-3-acetoxymethyl-7-azido-7-methoxyceph-3-em-4-carboxylates was obtained as a pale-yellow viscous oil which slowly crystallised (13.910 g, 36.2 mmole, 90.5%), λmax 248.5 nm, inflexion at 265 nm (ε7,500 and 7,060 respectively). The n.m.r. spectrum indicated the assigned isomer ratio. Crystallisation of a sample from ether and petroleum-ether (b.p. 60° to 80°) provided a sample of t-butyl(6R,7S)-3-acetoxymethyl-7-azido-7-methoxyceph-3-em-4-carboxylate as a white crystalline solid m.p. 77.5° to 78.5°(dec); [α]D -33.2°; t.l.c. Rf 0.51: λmax 247.5 nm, inflexion at 264.5 nm (ε 8,180 and 7,600 respectively). c)(i) A suspension of platinum oxide (99.4 mg) in dry dioxan (10 ml) was stirred under a dry nitrogen atmosphere. A slow stream of hydrogen was then bubbled through the suspension for 3 minutes. A solution of t-butyl (6R,7S)-3-acetoxymethyl-7-azido-7-methoxyceph3-em-4-carboxylate (98.7 mg, 0.257 mmole) in dry dioxan (5 ml) was added to the suspension and stirring continued for a total of 25 hours; the stream of hydrogen was passed for the first 71/2 hours and the last 2 hours of this period. The black solution-suspension was stirred with charcoal (2 g) for 10 minutes and then filtered through a bed of charcoal on kieselgel G (Merck) on Celite. The filtrate was evaporated to give a crude sample of the title compound, t.l.c. Rf 0.13.

Provenance & Evidence