Synthesis of (±)-penicillin and (±)-2-spirocyclopentanobisnorpenicillin systems

Phosphinimines as useful intermediates in the synthesis of 3-(acylamino)-.beta.-lactams

“…Esterification of 6 with diphenyldiazomethane afforded 7 (68%) which was S-methylated with methyl iodide and potassium carbonate to give the thioformimidate 8 (96%). Reaction of 8 with azidoacetyl chloride in the presence of triethylamine afforded, after chromatography, the trans-/3-lactam 9 (83%) and the cts-/3-lactam 10 (6%). The reaction between 2-heterosubstituted acetic acid chlorides, including azidoacetyl chloride, and S-alkylthioformimidates has been known to give exclusively fr<ms-/3-lactams;7,9,15 the formation of 10 constitutes the first case, in which a cis-/3-lactam was obtained directly from a thioformimidate.…”

“…To a solution of the acid 6 (5.5 g, 37.4 mmol) in dry acetone (100 mL) was added a solution of diphenyldiazomethane in acetone (40 mmol). After 2 h, the mixture was evaporated, and the residue was triturated with ether and then crystallized from CH2C12hexane to give the ester 7 (8.0 g, 68%): mp 112-114 °C; IR (KBr) 3300, 1720, 1540 cm4; NMR (CDClg) 1.58 (s, 6 ), 6.90 (s, 1 H), 7.30 (s, 10 H), 8.30 (br, 1 ), 9.30 (d, 1 H, J = 14 Hz). Anal.…”

“…A. To a solution of the azido lactam 9 (200 mg, 0.49 mmol) in benzene (4 mL) was added triphenylphosphine (133 mg, 0.5 mmol). After 15 min the solution was evaporated, and the residue was crystallized from ether to give the phosphinimine 11 (300 mg, 90%): mp 132 °C; IR (KBr) 1765, 1730 cm4; NMR (CDClg) 1.58 (s, 3 ), 1.71 (s) and 1.75 (s) (6 H), 4.33 (dd, 1 H, J = 1.5 and 26 Hz), 4.66 (d, 1 H, J = 1.5 Hz).…”

Bromination of cytosine derivatives

“…The loss of a C( 5)-H from 16 would give 8.14 However, nucleophilic attack of HO at C(6) of 16 could occur15 and (9) . E. Johns and G. DeBoer, Biochim.…”

“…At pH 7 a slight shoulder with reduced emM was observed without the appearance of a distinct new absorption maximum. In more basic media (pH [8][9], an absorption maximum at 280 nm appeared, and only the end absorption remained. Since hCyt derivatives generally exhibit Xmaz in the 240-260-nm region at these pHs, the lack of this absorption implies that deamination leading to the formation of 4b has occurred, and this product should display only end absorption.…”