Q: Do you think replacement of C2-alkyl chain by an aryl ring (lipophilic) would influence on SAR?
A: I am not aware of any Jaspine B analog where the whole alkyl chain has been replaced with an aryl ring, however, several groups (including us) have made C-2 modified analogs with a phenyl ring attached to the carbon chain (generally at the end of the chain). However, those analogs were mostly inactive.
Q: Do both Sphingomyelin synthase (SMS) 1 and 2 enzymes are essential for the biotransformation of ceramide to sphingomyelin? Is Jaspine B a dual inhibitor of SMS1 and SMS2?
A: Both SMS-1 and SMS-2 metabolize ceramide. SMS-1 mostly in the trans Golgi, while SMS-2 predominantly in plasma membrane. Jaspine B inhibits both to some extent.
Q: Why did you use two reducing agents (DIBAL-H & NaBH4)for the lactone reduction?
A: To reduce the use of excess DIBAL, which was otherwise creating difficulty in the aqueous work-up and subsequent recovery of the product diol.
Q: Have you observed any C2-epimerization in your synthetic route (Slide 14)? If so, how did you address the challenge to circumvent it?
A: After the publication of our first synthesis of Jaspine B (in 2005), there was some concern that the Wittig olefination route might be causing C-2 epimerization. However, our subsequent studies (2017 publication) have shown that it is not the case.
Q: Have you extended your total synthesis for 2-epi-Jaspine B, an isomer of the natural product Jaspine B? Does 2-epi-Jaspine B show any bioactivity?
A: We have not, however, a few other research groups have developed synthetic routes to the 2-epi analog and it has shown be active.
Q: Did you test the biological activity of guanidino derivative?
A: Yes, we did. Unfortunately, it was inactive.
Q: Would a 2-cycloalkyl ring tethered to the straight chain (keeping the chain length) confer interesting conformation that increases activity, what’s your prediction?
A: I do not recall seeing any C-2 cyclopropyl containing analogs, however some of the other groups have shown that C-2 olefinic Jaspine B could be active
Q: Did you get any co-crystals to modify more?
A: Unfortunately, SMS crystal structure has not yet been resolved.
Q: Does the apoptosis pathway of Jaspine B elicited in cells through only extrinsic or intrinsic route, or involve both routes?
A: Probably both, but I am not completely certain.
Q: Are Jaspine B and analogs active in resistant cell lines too?
A: In preliminary studies, Jaspine B has shown activity against some of the drug-resistant cell lines.
Q: Have you tested Jaspine B for activity against sphingosine kinases SPHK1 and SPHK2?
A: We have not, however, publications from other research groups have reported SphK1 inhibitory activity of Jaspine B and some modified analogs.