Abstract: A method of forming a thiohydantoin from an N-protected amino acid is described. The method employs a phosphate compound selected from the group consisting of(R.sub.1 O)(R.sub.2 O)P(.dbd.O)X and(R.sub.1 O)(R.sub.2 O)P(.dbd.O)--O--P(.dbd.O)(OR.sub.3)(OR.sub.4)to form acylphosphate moieties from the carboxyl groups of internal aspartic acid and glutamic acid residues and an acylphosphate moiety at a C-terminal carboxyl. The later acylphosphate, unlike the internal acylphosphates, spontaneously cyclizes to an oxazolone, which is less reactive with nucleophilic reagents. R.sub.1 and R.sub.2 are each alkyl, aryl, or alkaryl groups which are the same or different and which may be covalently linked to each other; R.sub.3 and R.sub.4 are each alkyl, aryl, or alkaryl groups which are the same or different and which may be covalently linked to each other; and X is a leaving group, such as chlorine or bromine, which is substantially unreactive towards thiohydantoins.

Abstract: A cartridge containing a dry polymer composition carrying trapped biopolymer subunits for use in synthesis of biopolymer chains provides a discrete unit for stepwise supply of subunits, such as protected amino acids, in an automated apparatus for biopolymer synthesis. The composition is swellable in organic solvent to release and supply the subunits to a growing biopolymer chain immobilized on a polymer support. An automated synthesizer uses the cartridges for sequential subunit supply and monitors conductivity of deprotection reagents to control cycling and timing of steps.

Abstract: A polymer composition having a biopolymer subunit entrapped in a swellable polymer matrix is described. The composition may be supplied in a disposable cartridge, for use in delivering a solution of the subunit in an automated biopolymer synthesis operation.