Academic literature on the topic 'Cis-dihydroxylation'

Masahito Ochiai developed (Org. Highlights, March 24, 2008) the iodosobenzene-mediated cleavage of alkenes to keto aldehydes. Thottumkara K. Vinod of Western Illinois University described (Org. Lett. 2010, 12, 5640) a modified protocol that delivered the keto acid 2. Chi-Ming Che of the University of Hong Kong established (J. Am. Chem. Soc. 2010, 132, 13229) a method for the preparative scale Fe-catalyzed cis dihydroxylation of an alkene 3. Ilhyong Ryu of Osaka Prefecture University devised (Synlett 2010, 2014) a practical procedure for the free radical addition of HBr to an alkene 5. Tetsuo Ohta of Doshisha University showed (Tetrahedron Lett. 2010, 51, 2806) that a Ru catalyst could add an aromatic acid to the internal carbon of a terminal alkene 7. Noriki Kutsumura and Takao Saito of the Tokyo University of Science found (Org. Lett. 2010, 12, 3316) conditions for bromination/dehydrobromination to convert 10 to 11. Tsuyoshi Taniguchi of Kanazawa University oxidized (J. Org. Chem. 2010, 75, 8126) the alkene 12 to the nitro alkene 13. Professor Taniguchi added (Angew. Chem. Int. Ed. 2010, 49, 10154) methyl carbazate to 14 to give the β-hydroxy ester 15. Philippe Renaud of the University of Bern effected (J. Am. Chem. Soc. 2010, 132, 17511) the free radical homologation of 16 to the azide 18. Daniel P. Becker of Loyola University described (Tetrahedron Lett. 2010, 51, 3514) the elegant diastereoselective Pd-catalyzed bis-methoxycarbonylation of 19 to the diester 20. Matthew S. Sigman of the University of Utah established (J. Am. Chem. Soc. 2010, 132, 13981) the oxidative Heck arylation of 21 to 23. F. Dean Toste of the University of California, Berkeley, found (Org. Lett. 2010, 12, 4728) that the intermediate in the gold-catalyzed alkoxylation of 24 could couple to an aryl silane 25 to give 26. Chun-Yu Ho of the Chinese University of Hong Kong used (Angew. Chem. Int. Ed. 2010, 49, 9182) a Ni catalyst to add styrene 27 to the alkene 24. Masahiro Miura of Osaka University effected (J. Org. Chem. 2010, 75, 5421) the oxidative coupling of 29 with styrene 27 to give the linear product 30.

The diterpene vinigrol 3, isolated from Virgaria nigra F-5408, has eluded total synthesis for more than 20 years. Attempts to construct the four-carbon bridge on a preformed cis-decalin have been unavailing. Phil S. Baran of Scripps/La Jolla solved (Angewandte Chem. Int. Ed. 2008, 47, 3054; J. Am. Chem. Soc. 2009, 131, 17066) this problem by adding the extra C-C bond of 1, which could then be cleaved in course of a Grob fragmentation, leading to 2. The preparation of 1 started with the dihydroresorcinol derivative 4. Diels-Alder addition of the ester 5 gave 6, with a modest 2:1 dr. Addition of allyl MgCl to the derived aldehyde 7 proceeded with 6:1 dr. The resulting triene was conformationally sufficiently constrained that cyclization to 8 proceeded at room temperature over 2 weeks, or more conveniently at 105°C for 90 minutes. With 8 in hand, oxidation to the ketone allowed installation of the additional methyl group of 9. Desilylation followed by OH-directed reduction set the relative configuration of 1 correctly for the Grob fragmentation to the Z -alkene 2. There were two remaining problems in the synthesis. The alkene of 2 had to be converted to the methylated tertiary alcohol, and the ketone had to be elaborated to the ene diol. Though seemingly straightforward, the congested tricyclic skeleton of 2 made many common transformations difficult. The solution to the first problem was found in the selective dipolar addition of bromonitrile oxide. Reduction of the ketone then enabled HO-directed hydrogenation of the alkene, which otherwise was resistant. Dehydration followed by reduction with LiAlH4 gave the desired methyl group bearing a primary amine, which was removed by free radical reduction of the corresponding isonitrile, to give 12. With 12 in hand, the end of the synthesis appeared to be in sight. In fact, the reduction of a variety of oxidized intermediates proved difficult. In the end, a sequence that did not require reduction proved effective. Dihydroxylation of 12 gave a diol, selective oxidation of which delivered the α-hydroxy ketone 13. Formation of the trisylhydrazone followed by Shapiro reaction gave the intermediate alkenyl anion, which was trapped with formaldehyde to give the long-sought vinigrol 3.

Fung-E Hong of the National Chung Hsing University devised (Adv. Synth. Catal. 2011, 353, 1491) a protocol for the oxidative cleavage of an alkene 1 (or an alkyne) to the carboxylic acid 2. Patrick H. Dussault of the University of Nebraska found (Synthesis 2011, 3475) that Na triacetoxyborohydride reduced the methoxy hydroperoxide from the ozonolysis of 3 to the aldehyde 4. Reductive amination of 4 can be effected in the same pot with the same reagent. Philippe Renaud of the University of Bern used (J. Am. Chem. Soc. 2011, 133, 5913) air to promote the free radical reduction to 6 of the intermediate from the hydroboration of 5. Robert H. Grubbs of Caltech showed (Org. Lett. 2011, 13, 6429) that the phosphonium tetrafluoroborate 8 prepared by hydrophosphonation of 7 could be used directly in a subsequent Wittig reaction. Dominique Agustin of the Université de Toulouse epoxidized (Adv. Synth. Catal. 2011, 353, 2910) the alkene 9 to 10 without solvent other than the commercial aqueous t-butyl hydroperoxide. Justin M. Notestein of Northwestern University effected (J. Am. Chem. Soc. 2011, 133, 18684) cis dihydroxylation of 9 to 11 using 30% aqueous hydrogen peroxide. Chi-Ming Che of the University of Hong Kong devised (Chem. Commun. 2011, 47, 10963) a protocol for the anti-Markownikov oxidation of an alkene 12 to the aldehyde 13. Aziridines such as 14 are readily prepared from alkenes. Jeremy B. Morgan of the University of North Carolina Wilmington uncovered (Org. Lett. 2011, 13, 5444) a catalyst that rearranged 14 to the protected amino alcohol 15. A monosubstituted alkene 16 is particularly reactive both with free radicals and with coordinately unsaturated metal centers. A variety of transformations of monosubstituted alkenes have been reported. Nobuharu Iwasawa of the Tokyo Institute of Technology employed (J. Am. Chem. Soc. 2011, 133, 12980) a Pd pincer complex to catalyze the oxidative monoborylation of 16 to give 17. The 1,1-bis boryl derivatives could also be prepared. Professor Renaud effected (J. Am. Chem. Soc. 2011, 133, 13890) radical addition to 16 leading to the terminal azide 18.

Chi-Ming Che of the University of Hong Kong devised (Chem. Commun. 2011, 47, 11204) a manganese catalyst for the enantioselective cis-dihydroxylation of electron-deficient alkenes such as 1. Christine Greck of Université de Versailles-St-Quentin effected (Tetrahedron Lett. 2012, 53, 1085) enantioselective alkoxylation of 3, remarkably without β-elimination. Keiji Maruoka of Kyoto University developed (J. Am. Chem. Soc. 2012, 134, 7516) an organocatalyst for the enantioselective anti addition of 5 to 6 to give 7. Barry M. Trost of Stanford University developed (J. Am. Chem. Soc. 2012, 134, 2075) a Mg catalyst for the enantioselective addition of ethyl diazoacetate to an aldehyde 8, and carried the adduct onto 9. Professor Maruoka designed (Angew. Chem. Int. Ed. 2012, 51, 1187) for the enantioselective addition of a ketone 10 to the alkynyl ketone 11 to give 12. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry found (Org. Lett. 2012, 14, 3108) that 14 could be added under very soft conditions to 13 to give the anti adduct 15. René Peters of the Universität Stuttgart added (Adv. Synth. Catal. 2012, 354, 1443) the azlactone formed in situ to 17 in a conjugate sense to give 18. Kaïss Aouadi and Jean-Pierre Praly of the Université de Lyon prepared (Tetrahedron Lett. 2012, 53, 2817) the nitrone 19 from the inexpensive (–)-menthone. Dipolar cycloaddition to a range of alkenes proceeded with substantial diastereocontrol, as illustrated for 20, which gave the crystalline adduct 21. Jeffrey S. Johnson of the University of North Carolina reduced (J. Am. Chem. Soc. 2012, 134, 7329) the α-keto ester 22 under equilibrating conditions to give the lactone 23. Claudio Palomo of the Universidad del País Vasco alkylated (J. Org. Chem. 2012, 77, 747) the aldehyde 24 with 25 to give the diester 26. Damien Bonne and Jean Rodriguez of Aix-Marseille Université added (Adv. Synth. Catal. 2012, 354, 563) the α-keto ester 27 to 28 in a conjugate sense to give 29. Glenn C. Micalizio of Scripps/Florida developed (Angew. Chem. Int. Ed. 2012, 51, 5152) a general strategy for the stereocontrolled construction of skipped-conjugate dienes such as 30.

The sedative alkaloid paliurine F 7 is a pentapeptide bridged by an arene. Gwilherm Evano of the Université de Versailles took advantage of this in his synthesis (Angew. Chem. Int. Ed. 2007, 46, 572) of 7, although it was necessary to prepare, from serine, one of the amino acid derivatives, the protected 3-hydroxyprolinol 2. The key step in the synthesis was the Cu-catalyzed intramolecular coupling of 5 to give the macrolactam 6. Deprotection and acylation then gave paliurine F 7. Lepadiformine 14, isolated from the tunicate Clavelina lepadiformis, shows moderate cytotoxicity, and is also a K+ channel blocker. The synthesis of 14 (Angew. Chem. Int. Ed. 2007, 46, 2631) by Donald Craig of Imperial College started with the aziridine 8, prepared from the corresponding epoxide. Opening of the protected aziridine with the anion of methyl phenyl sulfone set the stage for condensation of the dianion derived from 9 with the aldehyde 10, to give, with high diastereocontrol, the amine 11. Deprotection followed by cyclization then led to the activated ether 12. While the opening of 12 with an alkyl Grignard reagent proceeded with undesired inversion at the reacting center, opening with the alkynyl Grignard delivered mainly the desired 13. Reduction followed by oxidation, epimerization and reduction then gave lepadiformine 14. The Amaryllidaceae alkaloid 7-deoxypancratistatin 21 has potent antiviral activity. A challenge in the assembly of 21 is that the ring fusion is trans, less stable than the corresponding cis diastereomer. The synthesis of 21 (J. Org. Chem. 2007, 72, 2570) by Albert Padwa of Emory University started with 17, the preparation of which by the combination 15 and 16 he had previously reported in the course of his synthesis of lycoricidine (OHL December 11, 2006). Ester 17 had the desired trans ring fusion, but with an angular ester substituent that had to be removed. While it would be expected from the mechanism that Rh-mediated decarbonylation of an aldehyde would proceed with retention of absolute configuration, and this had been confirmed experimentally, this reaction had not been applied to such a challenging substrate. In the event, the transformation proceeded smoothly, to give the desired trans 19. Dehydration and dihydroxylation of 19 led to the cyclic sulfate 20, selective SN2 opening of which delivered 7-deoxypancratistatin 21.