Synthetic studies on altohyrtins (spongistatins): synthesis of the C15–C28 (CD) spiroacetal portion

Terauchi, Takeshi; Terauchi, Taro; Sato, Ippei; Tsukada, Tomoharu; Kanoh, Naoki; Nakata, Masaya

doi:10.1016/s0040-4039(00)00237-9

Cited by 30 publications

(10 citation statements)

References 24 publications

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“…On recommendation from a wonderful review by Pihko et al, [38] direct methods for conversion of 52 to 58 (i.e., treatment with HF·py, [39] aq HF [40] or HCl [41,42] ) were then investigated, which unfortunately provided little improvement. Following the work of Nakata, [43] however, TBS and acetonide deprotection performed with hydrogen fluoride pyridine complex afforded the polyol 59, which on treatment with CAN [44] revealed the target in 54 % yield over two steps (substituting CAN for PIFA [45] failed). Considering the effort required to drive cyclisation with acid promoters, and the fact that CAN performed this task extremely well, suggests that formation of the spiroacetal was www.chemeurj.org mediated by metal (namely cerium) templated preorganisation as precedented by Smith [41] and Evans.…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

Anticancer Agents from the Australian Tropical Rainforest: Spiroacetals EBC‐23, 24, 25, 72, 73, 75 and 76

Dong

Schill

Grange

et al. 2009

Chemistry A European J

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EBC-23, 24, 25, 72, 73, 75 and 76 were isolated from the fruit of Cinnamomum laubatii (family Lauraceae) in the Australian tropical rainforests. EBC-23 (1) was synthesized stereoselectively, in nine linear steps in 8 % overall yield, to confirm the reported relative stereochemistry and determine the absolute stereochemistry. Key to the total synthesis was a series of Tietze-Smith linchpin reactions. The novel spiroacetal structural motif, exemplified by EBC-23 (1), was found to inhibit the growth of the androgen-independent prostate tumor cell line DU145 in the mouse model, indicating potential for the treatment of refractory solid tumors in adults.

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Section: Wwwchemeurjorgmentioning

confidence: 99%

Anticancer Agents from the Australian Tropical Rainforest: Spiroacetals EBC‐23, 24, 25, 72, 73, 75 and 76

Dong

Schill

Grange

et al. 2009

Chemistry A European J

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“…Nakata and co-workers also had to rely on equilibration techniques in their synthesis of the CD spiroketal moiety of spongistatin. Removal of the dithioacetalization of 146 with ammonium cerium(IV) nitrate gave, with concomitant spiroketalization, a 1:3 mixture of spiroketals 147 and 148 (Scheme ) . Both possessed the nonanomeric configuration, but only spiroketal 147 corresponded to the natural product.…”

Section: 3 [66]-spiroketals Of Marine Origin331 CD Ring System Of The...mentioning

confidence: 99%

Nonanomeric Spiroketals in Natural Products: Structures, Sources, and Synthetic Strategies

Aho¹,

Pihko²,

Rissa³

2005

Chem. Rev.

364

158

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“…Using xylitol as the starting material to attain the desired meso stereochemistry, 5′DSCG-meso-diviol was synthesized with a modified synthetic route from that for the chiral stereoisomers (Scheme 2) because the same route was not effective for the meso isomer. The different steps included acetyl-bromination of tetraol 5c to give bromoacetate 6c, 40 epoxidation under basic conditions to generate diepoxide 7c that was purified by bulb-to-bulb distillation, 41 and iodination of diepoxide 7c to give diiodo diol 8c. Compound 8c was used to obtain the final product 1c under the same reaction conditions as that for the chiral isomers.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Stereochemical Control of Nonamphiphilic Lyotropic Liquid Crystals: Chiral Nematic Phase of Assemblies Separated by Six Nanometers of Aqueous Solvents

et al. 2013

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Unlike conventional thermotropic and lyotropic liquid crystals, nonamphiphilic lyotropic liquid crystals consist of hydrated assemblies of nonamphiphilic molecules that are aligned with a separation of about 6 nm between assemblies in an aqueous environment. This separation raises the question of how chirality, either from chiral mesogens or chiral dopants, would impact the phase as the assemblies that need to interact with each other are about 6 nm apart. Here, we report the synthesis of three stereoisomers of disodium chromonyl carboxylate, 5′DSCG-diviol, and the correlation between the molecular structure, bulk assembly, and liquid crystal formation. We observed that the chiral isomers (enantiomers 5′DSCG-(R,R)-diviol and 5′DSCG-(S,S)-diviol) formed liquid crystals while the achiral isomer 5′DSCG-meso-diviol did not. Circular dichroism indicated a chiral conformation with bisignate cotton effect. The nuclear Overhauser effect in proton NMR spectroscopy revealed conformations that are responsible for liquid crystal formation. Cryogenic transmission electron microscopy showed that chiral 5′DSCG-diviols form assemblies with crossings. Interestingly, only planar alignment of the chiral nematic phase was observed in liquid crystal cells with thin spacers. The homeotropic alignment that permitted a fingerprint texture was obtained only when the thickness of the liquid crystal cell was increase to above ∼500 μm. These studies suggest that hydrated assemblies of chiral 5′DSCG-diviol can interact with each other across a 6 nm separation in an aqueous environment by having a twist angle of about 0.22°throughout the sample between the neighboring assemblies.

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Synthetic studies on altohyrtins (spongistatins): synthesis of the C15–C28 (CD) spiroacetal portion

Cited by 30 publications

References 24 publications

Anticancer Agents from the Australian Tropical Rainforest: Spiroacetals EBC‐23, 24, 25, 72, 73, 75 and 76

Anticancer Agents from the Australian Tropical Rainforest: Spiroacetals EBC‐23, 24, 25, 72, 73, 75 and 76

Nonanomeric Spiroketals in Natural Products: Structures, Sources, and Synthetic Strategies

Stereochemical Control of Nonamphiphilic Lyotropic Liquid Crystals: Chiral Nematic Phase of Assemblies Separated by Six Nanometers of Aqueous Solvents

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