Total synthesis of (±)-coerulescine and (±)-horsfiline

• Mukund G. Kulkarni,
• Attrimuni P. Dhondge,
• Sanjay W. Chavhan,
• Ajit S. Borhade,
• Yunnus B. Shaikh,
• Deekshaputra R. Birhade,
• Mayur P. Desai and
• Nagorao R. Dhatrak

Beilstein J. Org. Chem. 2010, 6, 876–879, doi:10.3762/bjoc.6.103

• in clean cyclization leading to oxindole 9. After protecting the amide nitrogen with Boc, the oxindole 10 was treated with NaH, followed by ethyl chloroformate at 0 °C to give 11 in 80% yield. Oxidative cleavage of the allyl group was accomplished by catalytic osmium tetroxide and N-methylmorpholine

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• to a tricarboxylic acid core. Keywords: aminopyrans; carbohydrate mimetics; Lewis acids; lithiated enol ethers; nitrones; oxidative cleavage; stereodivergent synthesis; Introduction The pyran structural motif can be found in numerous bioactive natural products. Possible strategies towards their

• enantiopure aminopyrans. An additional option for the use of the enol ether moiety is oxidative cleavage [21]. Thus, benzyl protection of compound cis-5b followed by treatment of the resulting 19 with RuCl3 and NaIO4 gave the ten-membered ring lactone 20 by selective cleavage of the internal double bond

• moiety of trans-5a leading to products 13–15. Bromination of bicyclic dihydropyran trans-5b affording 16. Synthesis of epoxypyran 18 by bromination of cis-5d. Oxidative cleavage of dihydropyran 19 to lactone 20. Transformation of α-bromoketone 15 into nitrone 21 by an internal redox reaction

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

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

• 21 and oxidative cleavage of the resulting diol, the resultant aldehyde was treated with chiral allenylboronic ester to afford 22. The terminal epoxides 24 and 26 were prepared from the same intermediate 23. Coupling of 22 with 24 (or 26) in the same manner followed by hydrogenation and removal of

Radical cascades using enantioenriched 7-azabenzonorbornenes and their applications in synthesis

• David M. Hodgson and
• Leonard H. Winning

Beilstein J. Org. Chem. 2008, 4, No. 38, doi:10.3762/bjoc.4.38

• -disubstituted pyrrolidine (Scheme 6). This transformation was of interest because the pyrrolidine ring is a common nitrogen-containing motif in natural products and pharmaceutically relevant molecules [33]. Ruthenium tetraoxide was first examined as a reagent for the oxidative cleavage of the aromatic ring

• –oxidation with (−)-Ipc2BH to be determined by chemical correlation. Pyrrolidine 35 was independently prepared from (1R)-(−)-2-azabicyclo[2.2.1]hept-5-en-3-one (Vince’s lactam [36], 37) via reduction with LiAlH4, Boc-protection and oxidative cleavage [37] (Scheme 9). The pyrrolidines prepared from rearranged

• azacycle (+)-8 and lactam 37 were both dextrorotatory, confirming the provisional assignment of configuration that had been made by analogy with Laschat’s work [29]. Since attempts to effect RuO4-mediated oxidative cleavage of 2-azabenzonorbornene 8 employing periodic acid as the stoichiometric co-oxidant

End game strategies towards the total synthesis of vibsanin E, 3-hydroxyvibsanin E, furanovibsanin A, and 3-O-methylfuranovibsanin A

• Brett D. Schwartz,
• Craig M. Williams and
• Paul V. Bernhardt

Beilstein J. Org. Chem. 2008, 4, No. 34, doi:10.3762/bjoc.4.34

• ) by a Claisen rearrangment (via the silyl enol ether) was not high yielding and produced many side products. Ozonolysis of 25 afforded the acetone sidechain (i.e. 26) in acceptable yield (50%). Other methods to unmask the ketone functionality failed, for example, dihydroxylation followed by oxidative

• cleavage. Nevertheless, the acetone sidechain could be introduced in ~20% overall yield allowing end game functionalisation (as discussed below). α-Hydroxylation was next investigated. Considering the observed preference for regiospecific enolate formation in our system we devised a simple two pot

Total synthesis of the indolizidine alkaloid tashiromine

• Stephen P. Marsden and
• Alison D. McElhinney

Beilstein J. Org. Chem. 2008, 4, No. 8, doi:10.1186/1860-5397-4-8

• of the allylsilane to the N-acyliminium ion occurs through a chair-like transition state with the nascent alkene equatorially disposed. All that remained to complete the synthesis of tashiromine 1 was to effect the oxidative cleavage of the C5 vinyl substituent, then carry out a global reduction of

Combining two-directional synthesis and tandem reactions, part 11: second generation syntheses of (±)-hippodamine and (±)-epi-hippodamine

• Annabella F. Newton,
• Martin Rejzek,
• Marie-Lyne Alcaraz and
• Robert A. Stockman

Beilstein J. Org. Chem. 2008, 4, No. 4, doi:10.1186/1860-5397-4-4

• intermediate 7 and try to realise an improvement over our earlier work. This paper discloses two such improvements. The first of these is the conversion of dialkene 4 into the diacrylate derivative 6 . Originally this was achieved by oxidative cleavage of the two alkene moieties of 4 to form the rather

• immediately after isolation of the dialdehyde 5 (this was found to decompose upon storage, even at low temperature), and also the oxidative cleavage reaction produced large amounts of toxic osmium waste. During our recent synthesis of histrionicotoxin [11], we found that two-directional homologation of a

Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis

• Roger Hunter,
• Sophie C. M. Rees-Jones and
• Hong Su

Beilstein J. Org. Chem. 2007, 3, No. 38, doi:10.1186/1860-5397-3-38

• 6a (Scheme 2) with correct absolute configurations for castanospermine (C-8/C-8a), we sought to transform 6a into the target alkaloid, and in this paper report on the synthesis of an advanced intermediate towards this goal. Thus, adduct 6a underwent oxidative cleavage of the PMB protecting group

Do α-acyloxy and α-alkoxycarbonyloxy radicals fragment to form acyl and alkoxycarbonyl radicals?

• Dennis P. Curran and
• Tiffany R. Turner

Beilstein J. Org. Chem. 2006, 2, No. 10, doi:10.1186/1860-5397-2-10

• -butenylmagnesium bromide to 3-methylcyclohexenone followed by quenching with either acetyl chloride [26] or methyl chloroformate provided enol ester 9a (50%) and enol carbonate 9b (83%). Oxidative cleavage [27][28][29] and reduction then provided alcohols 10a and 10b, which were converted to iodides 11a and 11b