3-Alkanoyl-5-hydroxymethyl tetronic acid homologues: new inhibitors of HIV-1 protease. II. Structure determination.

Six new homologues of the 3-alkanoyl-5-hydroxymethyl tetronic acid (1 ~6) (Scheme 1) have been identified in extracts of the Actinomycete strain DSM7357 as inhibitors of HIV-1 protease. In the preceding paper1} we described the fermentation, isolation and biological properties of these secondary metabolites 1 ~6. The length and substitution pattern of the alkanoyl side chain of the tetronic acids (1~6) differ from a recently described naturally occurring tetronic acid2). Agglomerins A~D3) are tetronic acid derivatives with a different substitution of the butyrolactone ring, but exhibiting alkanoyl side chains of different length and branching. In this paper we will present the structure elucidation and physico-chemical properties of the tetronic acids 1 ~6. The FTIR spectrum of the tetronic acid 2, prepared as a potassium bromide pellet, is shown in Fig. 1. The spectrum is representative of all tetronic acid homologues and shows bands at 3429 (OH and moisture), 2920, 2851 (alkyl chain), 1720 (lactone C=O), 1647 (ketone C=O), 1564 (C=C), 1462 (mainly CH), 1367 (CH3), 1088, 1030 (C-O), 989, 779 and 721cm"1.