A concise enantioselective synthesis of the guaiane sesquiterpene (−)-oxyphyllol

• Martin Zahel and
• Peter Metz

Beilstein J. Org. Chem. 2013, 9, 2028–2032, doi:10.3762/bjoc.9.239

• the total synthesis of the anticancer guaiane (−)-englerin A. A regio- and diastereoselective Co(II)-catalyzed hydration of the olefin and a transannular epoxide opening were used as the key reactions. Keywords: asymmetric synthesis; hydration; natural products; terpenes; transannular epoxide opening

• 3 can be utilized to generate the isopropyl group, and a regioselective transannular epoxide opening would construct the oxygen-bridged bicyclic hydroazulene framework. Alcohol 3 was traced back to the known epoxy enone 4 that already served as an intermediate for the total synthesis of 5 [6]. As

• product 11. In contrast to the smooth transannular epoxide opening [13][14] encountered during the synthesis of 5, an attempted complete cyclization of 10 to give 11 during acidic work-up of the methylenation reaction led to considerable decomposition. Fortunately, catalytic amounts of ytterbium triflate

Synthesis of the tetracyclic core of Illicium sesquiterpenes using an organocatalyzed asymmetric Robinson annulation

• Lynnie Trzoss,
• Jing Xu,
• Michelle H. Lacoske and
• Emmanuel A. Theodorakis

Beilstein J. Org. Chem. 2013, 9, 1135–1140, doi:10.3762/bjoc.9.126

• this intermediate to Jones oxidation triggered a highly efficient oxidation–epoxide opening [93][94][95][96][97][98] reaction cascade [99][100] to construct the critical D-ring of 9 (46% yield, over 3 steps). Notably, this scalable approach rendered us several hundred milligrams of compound 9, paving

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

Synthesis and ring openings of cinnamate-derived N-unfunctionalised aziridines

• Alan Armstrong and
• Alexandra Ferguson

Beilstein J. Org. Chem. 2012, 8, 1747–1752, doi:10.3762/bjoc.8.199

• -opening protocols have been developed, synthesis of the starting NH-aziridine-2-carboxylates is multistep and low-yielding. Synthetic routes include Gabriel–Cromwell addition of ammonia to an enoate [16][17]; epoxide opening with azide, followed by ring closure [19]; and a sequence of olefin

Sonogashira–Hagihara reactions of halogenated glycals

• Dennis C. Koester and
• Daniel B. Werz

Beilstein J. Org. Chem. 2012, 8, 675–682, doi:10.3762/bjoc.8.75

• , overnight), whereas in the case of enyne 11b, under the same reaction conditions, only the triple bond was reduced to furnish enol ether 14e selectively. In three cases we further functionalized the 1-alkylated glycals by an epoxidation/epoxide-opening sequence [30][31][32][33]. Dimethyldioxirane (DMDO) was

• essential co-solvent in order to execute the Ni-catalyzed reduction. The enol ether double bond could be further hydroxylated by an epoxidation/epoxide opening sequence. Depending on the hydride source α- and β-configured alkyl-C-glycosides were obtained diastereoselectively in moderate yield. These

• epoxidation/epoxide opening sequence employing different hydride sources to afford 15a–15c. Supporting Information Supporting Information containing all experimental details and analytical data of all new compounds given in this article as well as their 1H and 13C NMR spectra is provided. Supporting

A straightforward approach towards combined α-amino and α-hydroxy acids based on Passerini reactions

• Ameer F. Zahoor,
• Sarah Thies and
• Uli Kazmaier

Beilstein J. Org. Chem. 2011, 7, 1299–1303, doi:10.3762/bjoc.7.151

• Ameer F. Zahoor Sarah Thies Uli Kazmaier Institute for Organic Chemistry, Saarland University, P.O. Box 151150, 66041 Saarbrücken, Germany 10.3762/bjoc.7.151 Abstract Complex amino acids with an α-acyloxycarbonyl functionality in the side chain are easily available through epoxide opening by

Amine-linked diglycosides: Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays

• Ian Cumpstey,
• Jens Frigell,
• Elias Pershagen,
• Tashfeen Akhtar,
• Elena Moreno-Clavijo,
• Inmaculada Robina,
• Dominic S. Alonzi and
• Terry D. Butters

Beilstein J. Org. Chem. 2011, 7, 1115–1123, doi:10.3762/bjoc.7.128

• difficult to synthesise; attempted Mitsunobu coupling failed, but we synthesised such amines by epoxide-opening. We did not achieve the formation of sec–sec linked secondary amines. The synthesis of a sec–sec amine-linked diglycoside structure by epoxide-opening was reported by Coxon [7], its formation

• being achieved in low yield (25%) under rather harsh conditions (autoclave, 140 °C), while a similar epoxide-opening reaction starting from a rather more complex substrate has been used to synthesise a pseudohexasaccharide in very low yield (12%) [8]. Kroutil et al. reported the synthesis of a number of

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• or stereoselective epoxidation followed by regioselective epoxide opening) produced the racemic iminocyclitols (18–20) in good overall yields (Scheme 3). In addition, Blechert showed that this method was more adaptable as it could also yield enantiopure 18–20, provided that racemization was avoided

• , separation of the diastereomers by flash chromatography was possible, affording the pure tetrahydropyridine derivative trans-133 in 74% yield. Successive epoxidations on enantiopure trans-133 and then 134, followed each time by regioselective epoxide opening (with a selenium–boron complex and water

• in a rather selective manner, a similar route to deoxymannojirimycin (63) and 1-deoxyallonojirimycin (66) did not achieve the same degree of selectivity, presumably due to difficulties in transforming the endocyclic double bond of the RCM product 72 into the targeted trans diols. Clean epoxide

Asymmetric synthesis of tertiary thiols and thioethers

• Jonathan Clayden and
• Paul MacLellan

Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68

• regioselective invertive epoxide opening. 1.1.3 Mitsunobu reactions The Mitsunobu reaction offers an operationally straightforward method for activating simple alcohols to invertive substitution, and it is widely used for constructing new stereodefined carbon–heteroatom bonds [24][25]. The Mitsunobu reaction

• tertiary thiols, the majority (for example, those involving epoxide opening or electrophilic attack on thio-substituted enolates) lead to thiols carrying further functionality in some form. Tertiary thiols without further functionality are still challenging, with organolithium-based alkylations and

Carbasugar analogues of galactofuranosides: α-O-linked derivatives

• Jens Frigell and
• Ian Cumpstey

Beilstein J. Org. Chem. 2010, 6, 1127–1131, doi:10.3762/bjoc.6.129

• electron-withdrawing group, the C3 benzyl ether. Ogawa has extensively used epoxide-opening reactions as a coupling method to access N- and O-linked pseudodisaccharides based on carbapyranoses [10]. The epoxides were opened by amines in uncatalysed reactions, or by alcohols under Lewis acidic, but more

• usually basic, conditions. An important general feature of epoxide opening in 6-membered rings is the tendency for trans-diaxial ring opening [11]. The existing substituents on the cyclohexane ring favour one of the two possible half-chair conformations (4H5 for 1 and 2). The principle of microscopic

• the α-talo product has a 2,3-cis and 1,4-cis substituent pattern, which could lead to some strain in the transition state, whereas β-galacto derivatives have an all trans substituent pattern. Should the epoxide-opening reaction proceed to give the α-talo configured C1-substituted products, then this

α,β-Aziridinylphosphonates by lithium amide-induced phosphonyl migration from nitrogen to carbon in terminal aziridines

• David. M. Hodgson and
• Zhaoqing Xu

Beilstein J. Org. Chem. 2010, 6, 978–983, doi:10.3762/bjoc.6.110

• epoxide-opening with H2NPO(OEt)2 followed by ring-closure was initially considered as a potential asymmetric route to N-phosphonate terminal aziridines 1. However, 1,2-epoxyhexane could not be successfully ring-opened with H2NPO(OEt)2 under a variety of conditions (NaH, KH, or NaH/DMPU in THF; (i-PrO)4Ti

Synthesis and crystallographic analysis of meso-2,3-difluoro-1,4-butanediol and meso-1,4-dibenzyloxy-2,3-difluorobutane

• Bruno Linclau,
• Leo Leung,
• Jean Nonnenmacher and
• Graham Tizzard

Beilstein J. Org. Chem. 2010, 6, No. 62, doi:10.3762/bjoc.6.62

• ; epoxide opening; gauche effect; organofluorine; vicinal difluoride; Introduction Selective fluorination of bioactive compounds is a widely employed strategy for the modification of their properties [1]. Fluorine atoms can be introduced to modulate the pKa of adjacent acidic and basic functional groups as

Synthesis of (3R,5R)-harzialactone A and its (3R,5S)-isomer

• Gowravaram Sabitha,
• Rangavajjula Srinivas,
• Sukant K. Das and
• Jhillu S. Yadav

Beilstein J. Org. Chem. 2010, 6, No. 8, doi:10.3762/bjoc.6.8

• . Epoxide opening with thioacetal and diastereoselective reductions are used as key reactions. Keywords: dithiane; harzialactone A; hydroxyl directed reduction; stereoisomer; Introduction Marine microorganisms such as bacteria, fungi, and microalgae have proved to be a rich source of structurally novel

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• at the other end of the molecule afforded 185, which was attached to lactone 186 by another epoxide opening, which produced the main structure 187. Finally, formation of the butenolide followed by removal of the silyl protecting groups finished the total synthesis of 15-epi-annonin I (181b

• ) 319 to afford 321. Introduction of the unprotected butenolide (as 323) by epoxide opening with lithiated 322 followed by selective reduction and deprotection afforded bullatacin. Total synthesis of rollidecins C and D Rollidecin C (324) and rollidecin