Structure of aminoglycoside 66-40 C, a novel unsaturated imine produced by Micromonospora inyoensis

Biomimetic synthesis and structural refinement of the macrocyclic dimer aminoglycoside 66-40C—the remarkably selective self-condensation of a putative aldehyde intermediate in the submerged culture medium producing sisomicin

“…1,2 Among the minor components produced by the same medium is a 4 0 ,5 0 -unsaturated pseudotrisaccharide which was designated as aminoglycoside 66-40C. 3 Degradative studies by Mallams and co-workers, then at the Schering-Plough Corporation, established the structure and stereochemistry of aminoglycoside 66-40C as the dimer shown as expression 2 (Fig. 1).…”

“…3 Critical experiments included careful osmometric determination of the molecular weight of aminoglycoside 66-40C compared to the parent sisomicin and its degradation to the monomer aldehyde 3 under strongly acidic conditions. 3 However, the authors made no allusion to the possibility of self-condensation of this monomeric aldehyde to regenerate aminoglycoside 66-40C. The dimer exhibited no antibacterial activity, instead it was used to access several 6 0 N-substituted sisomicins by reductive amination from the 6 0 -aldehyde (3).…”

“…1). 2,3,5 The unique features of aminoglycoside 66-40C make it an intriguing synthetic target. Detailed structural consideration suggests its formation from a non-enzymatic intermolecular double condensation of a putative 6 0 -aldehyde intermediate 3 onto the 3-amino group of a congener.…”

“…The physical, spectroscopic and chemical characteristics of the product were identical to those reported. 3 A quasi first order proton spectrum of aminoglycoside 66-40C in D 2 O is indicative of the prevalence of a preferred rigid macrocycle conformer. As originally presumed, homoand heteronuclear correlation experiments attest to the imine location on N-3 of the deoxystreptamine ring B.…”

The structure of aminoglycoside antibiotic 66-40G produced by Micromonospora inyoensis.

“…9 Isolation of Antibiotic 66-40G (4) A 5.5 g sample of sisomicin related substances, which was obtained by counter-current distribution of the mother liquors from a sisomicin crystallization, was dissolved in water and after adjustment to pH 6.1, applied to the top of a 3.3 cm x 142 cm Amberlite CG-50 column in the NH41-cycle. The column was subjected to stepwise elution beginning with water and then changing successively to 0.05 N NH40H, 0.1 N NH40H and 0.18 N NH40H, collecting 20-m1 fractions and monitoring by thinlayer chromatography using Analtech silica gel GF plates (250 microns) in the system chloroformmethanol -7 % ammonium hydroxide (1: 2: 1).…”