From a set of weakly potent lead compounds, using in silico screening and small library synthesis, a series of 2-alkyl-3-aryl-3-alkoxyisoindolinones has been identified as inhibitors of the MDM2-p53 interaction. Two of the most potent compounds, 2-benzyl-3-(4-chlorophenyl)-3-(3-hydroxypropoxy)-2,3-dihydroisoindol-1-one (76; IC(50) = 15.9 +/- 0.8 microM) and 3-(4-chlorophenyl)-3-(4-hydroxy-3,5-dimethoxybenzyloxy)-2-propyl-2,3-dihydroisoindol-1-one (79; IC(50) = 5.3 +/- 0.9 microM), induced p53-dependent gene transcription, in a dose-dependent manner, in the MDM2 amplified, SJSA human sarcoma cell line.

The design, synthesis and evaluation of 24 isoindolinones as potential inhibitors of the MDM2-p53 interaction is described. The most potent inhibitor NU8231 (ELISA: IC 50 = 5.3 ± 0.9 µM) displays cellular activity in human SJSA cells.

Dedicated to Professor Yoshito Kishi on the occasion of his 70th birthdayCytostatin (1) is a potent and selective inhibitor of protein phosphatase 2A that was isolated from the cultured broth of Streptomyces sp. by Ishizuka and co-workers (Scheme 1).[1] It inhibits lung metastasis of melanoma cells in mice and displays potent cytotoxic activity toward leukemia cell lines (inhibitory concentration; IC 50 = 42-65 nm). Ishizuka and coworkers assigned the two-dimensional structure (constitution) of cytostatin (1) by analysis of 1D and 2D NMR spectra. The relative configurations of C4-C6 and C9-C11 of cytostatin were assigned as syn at C4/C5 and C9/C10 and as anti at C5/C6 and C10/C11 by the research groups of Waldmann and Boger by comparison of key features of the 1 H NMR spectra of cytostatin with those of relevant models. [2,3] This approach lowered the number of structure candidates down to four, namely: 1 ss, 1 rs, 1 sr, and 1 rr.[4]Based on an analogy to fostriecin 2 [5] and related compounds (which share three stereocenters with 1), the research groups of Waldmann and Boger independently synthesized (4S,5S,6S,9S,10S,11S)-1 (hereafter called 1 ss), and concluded, by comparison of spectroscopic, physical, and biological properties, that this was the natural product.We have recently commented on the logic of proof and disproof of stereostructures by comparison of synthetic and natural samples.[6] If two or more stereoisomers of a natural product can reasonably be expected to have substantially identical spectra, then a rigorous assignment of the structure should include proof that the candidate isomer matches the natural product and, more importantly, proof that the other isomers do not. Acetogenins, such as the murisolins have very remote groups of stereocenters (10 or more methylene groups apart), so it can be expected that diastereomers might exhibit substantially identical spectra.[6] In contrast, the two groups of stereocenters in cytostatin (1) are only insulated by an ethylene group. Will enantiomers 1 ss and 1 rr have different spectra from their diastereomers 1 rs and 1 sr? To answer this question, and thereby to prove which three isomers were not cytostatin, we undertook the fluorous mixture synthesis [7,8] of all four isomers of 1.The fluorous mixture synthesis (FMS) strategy to make the four isomers of cytostatin is briefly outlined in Scheme 2. Late introduction of the triene is dictated by its chemical instability, so we followed the strategy of Bialy and Waldmann [2d] by planning to prepare four individual vinyl iodides 3 by coupling with alkenyl stannane 4.These four isomers are made over several steps from a single four-compound mixture of fluorous-tagged quasiisomers M-5 [9] ("quasi" because the compounds have different fluorous tags and are not true isomers [10] ). In turn, M-5 is made by coupling between fluorous-tagged quasiracemic aldehydes M-6 with quasiracemic keto phosphonates M-7 by a Horner-Wadsworth-Emmons (HWE) reaction.From the FMS standpoint, the configurations of the stereocenters ...

Dedicated to Professor Yoshito Kishi on the occasion of his 70th birthdayCytostatin (1) is a potent and selective inhibitor of protein phosphatase 2A that was isolated from the cultured broth of Streptomyces sp. by Ishizuka and co-workers (Scheme 1).[1] It inhibits lung metastasis of melanoma cells in mice and displays potent cytotoxic activity toward leukemia cell lines (inhibitory concentration; IC 50 = 42-65 nm). Ishizuka and coworkers assigned the two-dimensional structure (constitution) of cytostatin (1) by analysis of 1D and 2D NMR spectra. The relative configurations of C4-C6 and C9-C11 of cytostatin were assigned as syn at C4/C5 and C9/C10 and as anti at C5/C6 and C10/C11 by the research groups of Waldmann and Boger by comparison of key features of the 1 H NMR spectra of cytostatin with those of relevant models. [2,3] This approach lowered the number of structure candidates down to four, namely: 1 ss, 1 rs, 1 sr, and 1 rr.[4]Based on an analogy to fostriecin 2 [5] and related compounds (which share three stereocenters with 1), the research groups of Waldmann and Boger independently synthesized (4S,5S,6S,9S,10S,11S)-1 (hereafter called 1 ss), and concluded, by comparison of spectroscopic, physical, and biological properties, that this was the natural product.We have recently commented on the logic of proof and disproof of stereostructures by comparison of synthetic and natural samples.[6] If two or more stereoisomers of a natural product can reasonably be expected to have substantially identical spectra, then a rigorous assignment of the structure should include proof that the candidate isomer matches the natural product and, more importantly, proof that the other isomers do not. Acetogenins, such as the murisolins have very remote groups of stereocenters (10 or more methylene groups apart), so it can be expected that diastereomers might exhibit substantially identical spectra.[6] In contrast, the two groups of stereocenters in cytostatin (1) are only insulated by an ethylene group. Will enantiomers 1 ss and 1 rr have different spectra from their diastereomers 1 rs and 1 sr? To answer this question, and thereby to prove which three isomers were not cytostatin, we undertook the fluorous mixture synthesis [7,8] of all four isomers of 1.The fluorous mixture synthesis (FMS) strategy to make the four isomers of cytostatin is briefly outlined in Scheme 2. Late introduction of the triene is dictated by its chemical instability, so we followed the strategy of Bialy and Waldmann [2d] by planning to prepare four individual vinyl iodides 3 by coupling with alkenyl stannane 4.These four isomers are made over several steps from a single four-compound mixture of fluorous-tagged quasiisomers M-5 [9] ("quasi" because the compounds have different fluorous tags and are not true isomers [10] ). In turn, M-5 is made by coupling between fluorous-tagged quasiracemic aldehydes M-6 with quasiracemic keto phosphonates M-7 by a Horner-Wadsworth-Emmons (HWE) reaction.From the FMS standpoint, the configurations of the stereocenters ...

A previously developed 1,8-hydrogen atom transfer (HAT) reaction promoted by 6-O-yl alkoxyl radicals between the two pyranose units in Hexp-(1→4)-Hexp disaccharides has been extended to other systems containing at least a furanose ring in their structures. In Penf-(1→3)-Penf (A) and Hexp-(1→3)-Penf (B) disaccharides, the 1,8-HAT reaction and concomitant cyclization to a 1,3,5-trioxocane ring are in competition with radical β-scission of the C4-C5 bond and formation of dehomologated products. The influence of the stereoelectronic β-oxygen effect on the β-scission and consequently on the 1,8-HAT reaction has been studied using the four possible isomeric d-furanoses. d-xylo- and d-lyxo-derivatives afforded preferentially 1,8-HAT products, whereas d-arabino- and d-ribo-derivatives gave exclusively direct β-scission of the alkoxyl radical. When the 6-O-yl radical is on a pyranose ring, as occurs in Penf-(1→4)-Hexp (C), it has been shown to provide the cyclized products exclusively.