20-O-Acylcamptothecin Derivatives: Evidence for Lactone Stabilization
The Journal of Organic Chemistry2000Vol. 65(15), pp. 4601–4606
Citations Over TimeTop 17% of 2000 papers
Hong Zhao, Chyi Lee, Prakash Sai, Yun H. Choe, Michelle Boro, Annapurna Pendri, Shuiyun Guan, Richard B. Greenwald
Abstract
Convincing UV and NMR spectrophotometric evidence is presented which demonstrates that at physiological pH, 7.4, 20-O-acyl derivatives of camptothecin (CPT) are substantially more stable in the lactone form than the 20-OH parent. Additionally, it was determined by HPLC analysis that the lactone ring of a 20-O-ether derivative of CPT underwent endocyclic ring opening at pH > or =8.5, while the lactone ring of 20-O-acyl CPT derivatives remained unaffected. PEG (and other smaller alkyl) 20-O-acyl-CPT derivatives released native CPT at pH > 9.5, which arises from exocyclic cleavage, thus precluding isolation of any open CPT acyl PEG (or alkyl) carboxylate forms.
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