Molecular Design of Nobel DNA Alkylating Agent at GG step

我们用d -异抗坏血酸及其三种非对映异构体合成了环氧萘吡喃酮。含有5‘XGT3’和5‘TGY3’的odn的DNA被(11R, 13R)-环氧化物烷基化，其中X和Y是任意核苷酸碱基，发生在除5‘TGC3’序列的G外的所有G个残基上。而其他三种非对映异构体的G烷基化活性较弱。药物- g加合物的微分1H NMR NOE证实了G-N7在环氧化物碳上的烷基化，并伴随环氧化物的S_N2环开孔。通过高效液相色谱法对G烷基化效率进行了定量分析，结果表明G烷基化敏感性依次为TGGT【近似等于】CGT >> TGA > AGT > TGT >> TGC。该顺序与黄曲霉毒素B_1氧化物和卡普里霉素A_3的顺序完全一致，表明这些DNA烷基化剂的序列选择性与结构无关，而很可能是由于DNA序列的固有性质。我们发现所得的G烷基化敏感性顺序与计算的含G序列HOMO能级完全吻合。这些结果表明，我们的药物是一种独特的分子探针，可以通过众所周知的G烷基化化学对含G序列的HOMO水平进行排序，并表明电荷中性插入物的插入是一个HOMO控制的过程。

We have synthesized naphthopyranone epoxide from D-isoascorbic acid together with its three diastereoisomers. DNA alkylation of ODNs containing 5'XGT3' and 5'TGY3' by (11R, 13R)-epoxide, where X and Y are any nucleotide bases, occurred at all G residues except at G of 5'TGC3' sequence. In contrast, other three diastereoisomers showed only weak G alkylation activity. Differential ^1H NMR NOE of drug-G adduct confirmed the G-N7 alkylation at the epoxide carbon with concomitant S_N2 ring opening of the epoxide. Quantitative HPLC analysis of G alkylation efficiency by showed the order of G alkylation susceptibility as TGGT 【approximately equal】 CGT >> TGA > AGT > TGT >> TGC.The order was fully consistent with those reported for aflatoxin B_1 oxide and kapurimycin A_3, suggesting that the sequence selectivity observed for these DNA alkylating agents is not structure dependent but most likely due to the intrinsic property of DNA sequences. We found that the order of G alkylation susceptibility obtained completely matched with the calculated HOMO energy level of G-containing sequences. These results underscore that our drug is a unique molecular probe for ranking HOMO level of G-containing sequences by well-known G alkylation chemistry and suggests that the intercalation of charge neutral intercalators is a HOMO-controlled process.