Solution Conformational Analysis of 2′‐Amino‐2′‐Deoxyadenosine, 3′‐Amino‐3′‐Deoxyadenosine and Puromycin by Pulsed Nuclear‐Magnetic‐Resonance Methods

Abstract

The solution conformation of 2''-amino-2.sbd.deoxyadenosine, 3''-amino-3''-deoxyadenosine and 3''-amino-3''-deoxy-6-N,N-dimethyladenosine were determined by NMR in aqueous and ammonia solutions. The analysis of the ribose moiety is based on the 2-state S .dblarw. N model of Altona and Sundaralingam. Longitudinal proton relaxation time and nuclear Overhauser enhancement measurements were carried out to characterize the orientation of the base relative to the ribose. 3''-Amino-3''-deoxyadenosine and 3''-amino-3''deoxy-6-N,N-dimethyladenosine probably exist in solution preferentially in the N-anti-g+ conformations. On the other hand, 2''-amino-2''-deoxyadenosine adopts the S-syn-g+/t conformation families. It appears that the base is restricted to the anti conformation in the first 2 compounds, while in 2''-amino-2''-deoxyadenosine, 1/3 of the molecules in the S state are in the anti range. These studies corroborate the previously proposed correlations between the N state of the ribose and the anti orientation of the base and between the S state of the ribose and the syn orientation of the base.