Synthesis of 4-Amino-2(5<i>H</i>)-furanones through Intra- and Intermolecular Nitrile Addition of Ester Enolates. Construction of Carbon Framework of an Antitumor Antibiotic Basidalin
ester group, deprotection, olefin isomerization and lactonization all in a single operation. The other is base-induced ringclosure of α-acyloxy nitriles. The two methods are applied to construction of the carbonframework of an antitumor antibiotic basidalin.
Acetonecyanohydrin (1) yields on acylation and ring closure with anhydrides and perchloric acid. 2-oxazolin-4-onium perchlorates 5a, 5c or 5d. The same perchlorates (5a, 5b) may be obtained under similar conditions from acyloxy-nitriles (2) or -amides (4). Perchlorates 5 may be deprotonated in pyridine to 2-oxazolin-4-ones (6), but in aqueous solution they undergo ring opening to acyloxy-amides 4a
(57) The instant invention is directed to an osmotic pump comprising:
(a) at least one active agent surrounded by
(b) a water insoluble wall, having a fluid permeability of 6.96 x 10-18 to 6.96 x 10-14cm3 sec/g and a reflection coefficient of less than 1, prepared from:
(i) a polymer permeable to water but impermeable to solute, and
(ii) 0.1 to 60% by weight, based on the total weight of (i) and (ii), of at least one pH insensitive pore forming additive dispersed throughout said wall.