Regiochemical Variations in Reactions of Methylcubane with tert-Butoxyl Radical, Cytochrome P-450 Enzymes, and a Methane Monooxygenase System
摘要:
Reactions of methylcubane (1) with the tert-butoxyl radical (t-BuO.), with cytochrome P-450 enzymes, and with a methane monooxygenase (MMO) system have been studied. For the purpose of product characterization, authentic samples of 2-methylcubyl and 4-methylcubyl derivatives were prepared. 2-Methylcubanecarboxylic acid (9b) is a new compound prepared from cubanecarboxylic acid. The key synthetic reactions were (1) metalation and subsequent iodination of the 2-position of (diisopropylcarbamoyl)cubane to effect the initial functionalization, (2) lithium-for-iodine exchange and methylation followed by reduction to give 2-methyl-1-[(diisopropylamino)methyl]-cubane, and (3) dimethyldioxirane oxidation of this amine to give 9b. The known 4-methylcubanecarboxylic acid (9d) was prepared here by a route related to that employed for 9b. Reactions of acids 9b and 9d with methyllithium gave the corresponding methyl ketones which were oxidized by m-chloroperoxybenzoic acid to provide authentic samples of 2- and 4-methylcubanol acetates (3b and 3d). Reaction of 1 with t-BuO(.) in the presence of 2,2,5,5-tetramethylisoindole-N-oxyl radical (TMIO(.)) at 40-55 degrees C gave mainly cube-substituted products in confirmation of the report (Della, E. W.; Head, N. J.; Mallon, P.; Walton, J. C. J. Am. Chem. Sec. 1992, 114, 10730) that hydrogen atom abstraction by the electrophilic alkoxyl radical at low temperature occurs at the cubyl C-H positions. In a competition experiment at 42 degrees C, methylcubane was at least 3.5 times more reactive toward t-BuO(.) than cyclohexane, indicating that the cubyl positions in 1 are greater than or equal to 40 times more reactive than the methyl positions in 1 (per hydrogen) toward the alkoxyl radical. Oxidation of 1 by enzymes gave alcohol products that were converted to their acetate derivatives for identification and quantitation. Microsomal cytochrome P-450 enzymes from rat and the rat purified P-450 isozyme CYP2B1 hydroxylated 1 at all positions, whereas the reconstituted MMO system from Methylococcus capsulatus (Bath) hydroxylated 1 only at the methyl position. The differences in regioselectivity suggest that the transition states for hydrogen abstraction by the alkoxyl radical and for enzyme-catalyzed hydroxylation differ considerably. The results are consistent with a model for concerted enzyme catalyzed hydroxylation of 1 involving ''side-on'' approach to the C-H bond of substrate.
The cubane paradigm in bioactive molecule discovery: further scope, limitations and the cyclooctatetraene complement
作者:Sevan D. Houston、Tyler Fahrenhorst-Jones、Hui Xing、Benjamin A. Chalmers、Melissa L. Sykes、Jeanette E. Stok、Clementina Farfan Soto、Jed M. Burns、Paul V. Bernhardt、James J. De Voss、Glen M. Boyle、Maree T. Smith、John Tsanaktsidis、G. Paul Savage、Vicky M. Avery、Craig M. Williams
DOI:10.1039/c9ob01238a
日期:——
antibiotics (cefaclor, penicillinG) and antihistamine (diphenhydramine), a smooth muscle relaxant (alverine), an anaesthetic (ketamine), an agrochemical instecticide (triflumuron), an antiparasitic (benznidazole) and an anticancer agent (tamibarotene). This investigation highlights the scope and limitations of incorporating cubane into bioactive molecule discovery, both in terms of synthetic compatibility
A Protocol for an Iodine–Metal Exchange Reaction on Cubane Using Lithium Organozincates
作者:Yumi Kato、Craig M. Williams、Masanobu Uchiyama、Seijiro Matsubara
DOI:10.1021/acs.orglett.8b03721
日期:2019.1.18
The iodine–metal exchangereaction on cubane was examined using various lithium organozincates. Among these, the dianionic zincate, n-Bu4ZnLi2, gave optimum results. The resulting cubyl metal species could be converted into various cubane derivatives via addition reactions with electrophiles, such as an organohalide or aldehyde. The potential functional group tolerance of organozincates lends this
使用各种有机锌锂检查了古巴对碘-金属的交换反应。其中,双阴离子锌酸盐n- Bu 4 ZnLi 2给出最佳结果。可以通过与亲电试剂(例如有机卤化物或醛)进行加成反应,将生成的立方金属物种转化为各种古巴衍生物。有机锌酸盐的潜在官能团耐受性使该方案适用于多官能化古巴衍生物的合成。
Cubane Chirality via Substitution of a “Hidden” Regular Tetrahedron
class of chiral molecules. In pursuit of this endeavor, we prepared 1,3-dibromo-4-deuteriocubane-N,N-diisopropylcarboxamide, which upon treatment with zincates affords 1,3,5-trisubstituted cubanes via simultaneous two-position substitution reactions. The proposed chiral attributes of this stereogeometric class were confirmed by enantiomeric resolution of a p-bromobenzyl derivative using chiral HPLC.
Unmasking Inherent Chirality within the Cubane Skeleton
作者:Nana Yoshino、Yumi Kato、Yukako Shimada、Craig M. Williams、Seijiro Matsubara
DOI:10.1002/ijch.202100013
日期:2021.7
Cubane, a hexahedral hydrocarbon, can be converted into an asymmetric molecule with a minimum of three substituents. The resulting chiral cubane can be used as a pharmacophore or a chiral ligand. Starting from the cubane carboxamide, the 1,2,3-substituted compound was synthesized by sequential ortho-metalation. The 1,3,5-substituted compound was synthesized by combining site-selective halogenation
Chiral Auxiliary-Directed Site-Selective Deprotonation of the Cubane Skeleton
作者:Hiyori Takebe、Nana Yoshino、Yukako Shimada、Craig M. Williams、Seijiro Matsubara
DOI:10.1021/acs.orglett.2c03659
日期:2023.1.13
The first diastereoselective synthesis of trisubstituted cubanes was achieved using a chiral auxiliary. To establish chirality within the cubane skeleton, at least three substituents must be introduced at the appropriate positions. Ready conversion of cubane carboxylic acid to a chiral amide followed by sequential ortho-selective deprotonations and electrophilic trapping afforded the corresponding