DNA decamers containing 2-aminoadenosine were synthesized. Oligonucleotide duplexes including the 2 NH2A-T base pairs were prepared and their Tm profile examined. Contrary to expectation, elevation of the Tm value by the 2 NH2 group is very small in DNA/RNA duplexes. From the CD spectra measurement, we assume that the distortion of the B-DNA structure caused by scattered DNA/RNA base pairing diminishes the efficient hydrogen bonding and base stacking of the duplexes. It was also found that the DNA duplexes containing 2-aminoadenosine hybrids are considerably resistant to ribonuclease T2 or nuclease P1 digestion.
Vulpinic acid has been isolated from sporophores of Pulveroboletus ravenelii, its first reported occurrence in a Basidiomycete. Permethyl ethers of methyl xerocomate and methyl atromentate and its corresponding monochloro derivatives are produced by P. auriflammeus of Japanese origin.
Two deoxynucleoside analogues, 1-(2-deoxy-β-D-ribofuranosyl)-2-oxo-4-imidazoline-4-carbox-amide (1) and 5-carbamoyl-2′-deoxyuridine (2), were synthesized and incorporated into decamer deoxynucleotides, which were hybridized to their complementary strands. The duplices in which 1 paired with A or G showed higher melting temperatures (Tm's) than those containing G -T or A -C mismatch, although lower than the Tm of intact totally complementary duplex. The incorporation of 2 into a strand resulted in extreme destabilization of the duplex.
The close genetic relationship of the mushrooms Retiboletus griseus and R. nigerrimus is supported by the occurrence of the orange-yellow retiboletic acid, resp. its methyl ester, in both species. The structures of these highly substituted pulvinic acid derivatives have been elucidated by spectroscopic investigations. R. nigerrimus also contains two N-protocatechuyl-L-phenylalaninol derivatives, nigerrimin A and B, the first reported occurrence of such compounds in nature. Their configuration was established by the synthesis of nigerrimin B