Erik de Vroom

Enzymatic synthesis of β-lactam antibiotics using penicillin-G acylase in frozen media

Penicillin‐G acylase (EC 3.5.1.11) from Escherichia coli catalyzed the synthesis of various β‐lactam antibiotics in ice at −20°C with higher yields than obtained in solution at 20°C. The initial ratio between aminolysis and hydrolysis of the acyl‐enzyme complex in the synthesis of cephalexin increased from 1.3 at 20°C to 25 at −20°C. The effect on the other antibiotics studied was less, leading us to conclude that freezing of the reaction medium influences the hydrolysis of each nucleophile‐acyl‐enzyme complex to a different extent. Only free penicillin‐G acylase could perform transformations in frozen media: immobilized preparations showed a low, predominantly hydrolytic activity under these conditions.

Penicillin acylase-catalyzed synthesis of ampicillin in "aqueous solution-precipitate" systems. High substrate concentration and supersaturation effect

Abstract Penicillin acylase-catalyzed ampicillin synthesis via acyl group transfer in aqueous solution is highly dependent on the initial substrate concentration. The solubility of one substrate, 6-aminopenicillanic acid (6-APA), can be advantageously enhanced by the presence of acyl donor, the second substrate. Furthermore, a comparison of enzymatic synthesis in homogeneous solution with synthesis in a heterogeneous system having partially undissolved reactants, reveals major advantages for the latter approach. In this “aqueous solution–precipitate” system, accumulation of both products, ampicillin and d -(−)-phenylglycine, proceeds through the formation of their supersaturated solutions. Subsequent precipitation of the product ampicillin positively influences the efficiency of the biocatalytic process. As a result, ampicillin synthesis proceeds in 93% conversion on 6-APA and in 60% conversion on d -(−)-phenylglycine methyl ester.

Synthesis of Penicillin N and Isopenicillin N

Abstract Enantiomeric 2-(N-allyloxycarbonyl)aminoadipic acid 1-allyl esters were obtained from the corresponding 2-(N-trityl)aminoadipic acid diallyl esters following selective hydrolysis of the allyl 6-ester group and subsequent exchange of the trityl group by the allyloxycarbonyl function. The resulting monoacids were used to acylate 6-aminopenicillanic acid allyl ester using a carbodiimide-mediated coupling. The products, the l - and d -isomers of 6-[6-(2-(N-allyloxycarbonyl) aminoadipyl)]aminopenicillanic acid diallyl ester were deprotected in one step by catalytic allyl transfer using tetrakis-(triphenylphosphine)palladium(0), to afford isopenicillin N and penicillin N, respectively. The presented straightforward route to penicillin N and isopenicillin N is uniquely compatible with the sensitive nature of the condensation products and gives entry to a new and high yielding procedure that is superior to existing approaches.

A New Convenient Synthesis of 3-Carboxycephems Starting from 7-Aminocephalosporanic Acid (7-ACA)

New convenient syntheses of 3-carboxycephems starting from 7-ACA are reported. All three possible cephem derivatives with respect to the position of the double bond in the six-membered ring and oxidation state of the sulfur atom have been synthesized in high overall yield.

Enzymatic coupling using a mixture of side chain donors affords a greener process for ampicillin

The penicillin acylase catalyzed synthesis of ampicillin, via acylation of 6-aminopenicillanic acid with D-phenylglycine amide, is accompanied by the formation of the hydrolysis product D-phenylglycine. The recycling of D-phenylglycine in the process viaD-phenylglycine methyl ester hydrochloric acid salt was investigated. The efficiency of a resulting innovative process, using both the amide and ester as donors, was compared with the process without recycling and that with recycling via the amide. Recycling via the ester, in a mixed donor coupling, resulted in the most economic process with respect to the use of chemicals and the production of waste.

Cephalosporanic acid 7β-alkylideneammonio salts

Abstract Reaction of 7β-aminocephalosporanic acid derivatives 2 with ketones under acidic conditions leads to the unprecedented formation of alkylideneammonio salts 4. 3′-Halogenated cephalosporanic acid derivatives bearing an unprotected carboxylgroup are normally considered to be sensitive intermediates that can easily undergo lactonization. However, these compounds are suprisingly stable when transformed into their 7β-alkylideneammonio salts and can thus be elegantly used as versatile intermediates in cephalosporin chemistry.