Prins fluorination cyclisations: Preparation of 4-fluoro-pyran and -piperidine heterocycles

• Guillaume G. Launay,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2010, 6, No. 41, doi:10.3762/bjoc.6.41

• the Prins fluorination products, pyran 5m was subjected to hydrogenolysis [23] as illustrated in Scheme 2. This resulted in the efficient conversion to the corresponding open chain compound 3-fluoro-5-phenylpentyl acetate (7). The structural diversity of the Prins fluorination reaction was extended

Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

• Andreas Speicher,
• Timo Backes,
• Kerstin Hesidens and
• Jürgen Kolz

Beilstein J. Org. Chem. 2009, 5, No. 71, doi:10.3762/bjoc.5.71

• stereochemical correlation between isoplagiochin C (1) and isoplagiochin D (2) was also confirmed experimentally by hydrogenolysis of enantiopure samples of (PA)-1 to give and (PA)-2 (Scheme 1), and of (MA)-1 to give and (MA)-2, respectively, without any racemization [14]. The natural compounds isoplagiochin D

An efficient partial synthesis of 4′-O-methylquercetin via regioselective protection and alkylation of quercetin

• Nian-Guang Li,
• Zhi-Hao Shi,
• Yu-Ping Tang,
• Jian-Ping Yang and
• Jin-Ao Duan

Beilstein J. Org. Chem. 2009, 5, No. 60, doi:10.3762/bjoc.5.60

• available for the cleavage of such diphenylmethylene ketals: hydrogenolysis or hydrolysis. Under hydrogenation conditions the ketal could be cleaved selectively. The best results were obtained with 10% palladium on carbon as the catalyst in THF/EtOH. TLC showed that the reaction was complete after 8 h. This

Novel banana-discotic hybrid architectures

• Hari Krishna Bisoyi,
• H. T. Srinivasa and
• Sandeep Kumar

Beilstein J. Org. Chem. 2009, 5, No. 52, doi:10.3762/bjoc.5.52

• 50 mL of water and then extracted with chloroform, the chloroform layer was washed with 50 mL of water followed by drying over anhydrous sodium sulfate. The solvent was removed to yield a viscous oily residue 3 which was taken as such for hydrogenolysis. Preparation of 4-{12-[3,6,7,10,11-pentakis

2-Phenyl- tetrahydropyrimidine- 4(1H)-ones – cyclic benzaldehyde aminals as precursors for functionalised β²-amino acids

• Markus Nahrwold,
• Arvydas Stončius,
• Anna Penner,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2009, 5, No. 43, doi:10.3762/bjoc.5.43

• , this structural modification would facilitate a final release of the β2-amino acid by hydrogenolysis of all remaining benzyl-type N-protective groups. Results and Discussion Cyclocondensation of benzaldehyde and β-amino acid amides to 2-phenyl-tetrahydropyrimidine-4(1H)-ones is problematic, since

• N1-Cbz-protective group of 4 can be chemoselectively cleaved by carefully monitored hydrogenolysis on 10% Pd/C in dry THF solution. The pure fully deprotected tetrahydropyrimidinone rac-7 was obtained after recrystallisation from ethyl acetate. Although 7 proved to be stable under inert gas

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

• alcohol 215. Tosylation and hydrogenolysis with LiEt3BH removed the C-30 OTs group affording the SEM ether 216. The remaining steps for the completion of total synthesis of asiminecin were carried out along the lines described for asiminocin. Total synthesis of (+)-(30S)-bullanin (+)-Bullanin was isolated

• employed the (R)-α-OSEM allylic stannane 261 reaction with the dialdehyde 262 obtained from (S,S)-diethyl tartrate to afford the bis-adduct 263 (Scheme 36). Treatment of 263 with TBAF led to the core bis-THF intermediate, diol 264. Mono tosylation and subsequent hydrogenolysis with LiBEt3H gave alcohol 265

The first preparative solution phase synthesis of melanotan II

• Vladimir V. Ryakhovsky,
• Georgy A. Khachiyan,
• Nina F. Kosovova,
• Elena F. Isamiddinova and
• Andrey S. Ivanov

Beilstein J. Org. Chem. 2008, 4, No. 39, doi:10.3762/bjoc.4.39

• coupled with another dipeptide 5 using a combination of N,N′-dicyclohexylcarbodiimide (DCC) and N-hydroxynorbornene-2,3-dicarboximide (HONb) to yield a tetrapeptide product 7. The latter was subjected to catalytic hydrogenolysis leading to tetrapeptide salt 8 with an uncapped N-terminus. Hydrochloride of

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• -unsaturated ester, which was subjected to Pearlman hydrogenolysis of the benzyl group and selective catalytic reduction of the non-conjugated olefin with iridium black. The latter step proceeded in a predominately syn manner to afford intermediate 12, which was oxidized to cyclopentadiene 13 through TBS

• ether 80 was prepared via ethylene glycol protection, saponification, alkylation by prenyl bromide, hydrogenation and acetonide cleavage. Two other analogs were assembled from 70 by LiOH hydrolysis of the benzoate ester and Pd/C hydrogenolysis of the benzyl one. While biological tests indicated that

Analogues of amphibian alkaloids: total synthesis of (5R,8S,8aS)-(−)-8-methyl- 5-pentyloctahydroindolizine (8-epi-indolizidine 209B) and [(1S,4R,9aS)-(−)-4-pentyloctahydro- 2H-quinolizin- 1-yl]methanol

• Joseph P. Michael,
• Claudia Accone,
• Charles B. de Koning and
• Christiaan W. van der Westhuyzen

Beilstein J. Org. Chem. 2008, 4, No. 5, doi:10.1186/1860-5397-4-5

• slowly to a stirred suspension of the hydride in diethyl ether (Scheme 4). If the order of addition were reversed, the best yield obtained was 48%. The amino alcohol was protected as its tert-butyl(dimethyl)silyl ether (−)-31 (99%) before hydrogenolysis of the benzyl groups over Pearlman's catalyst in

A divergent asymmetric approach to aza-spiropyran derivative and (1S,8aR)-1-hydroxyindolizidine

• Jian-Feng Zheng,
• Wen Chen,
• Su-Yu Huang,
• Jian-Liang Ye and
• Pei-Qiang Huang

Beilstein J. Org. Chem. 2007, 3, No. 41, doi:10.1186/1860-5397-3-41

• -cleavage/cyclication, and O-debenzylation. In searching for a more concise method, amino alcohol 8 was mesylated (MsCl, NEt3, 0 °C) and the resultant labile mesylate 12 was subjected to catalytic hydrogenolysis (H2, l atm, 10% Pd/C, r.t.), which gave (1S,8aR)-1-hydroxyindolizidine (ent-3) in 60% overall

An asymmetric synthesis of all stereoisomers of piclavines A1-4 using an iterative asymmetric dihydroxylation

• Yukako Saito,
• Naoki Okamoto and
• Hiroki Takahata

Beilstein J. Org. Chem. 2007, 3, No. 37, doi:10.1186/1860-5397-3-37

• ])-16 in 94%. It is impossible to utilize hydrogenolysis due to reactivity of the acetylene unit. Indeed, the N-protecting group exchange of benzyloxycarbonyl (Cbz) for 2,2,2-trichloroethoxycarbonyl (Troc) in 17 was examined. The use of basic reagents such as Ba(OH)2[11] and KOH[12] failed to afford

A convenient allylsilane- N-acyliminium route toward indolizidine and quinolizidine alkaloids

• Roland Remuson

Beilstein J. Org. Chem. 2007, 3, No. 32, doi:10.1186/1860-5397-3-32

• with one equivalent of stannic chloride resulted in the formation of 10 via the acyliminium ion intermediate 11. Subsequent oxidation of alcohol 10 with pyridinium dichromate, then catalytic hydrogenation (H2 over Pd/C) of ketone 12 induced hydrogenolysis of the CBz group, reduction of the double bond

Diastereoselective synthesis of some novel benzopyranopyridine derivatives

• Pradeep K. Mohakhud,
• Sujeet M. R. Kumar,
• Vasanth M. R. Kumar,
• Ravi M. R. Kumar,
• Moses D. R. Babu,
• Vyas D. R. K and
• Om D. R. Reddy

Beilstein J. Org. Chem. 2006, 2, No. 25, doi:10.1186/1860-5397-2-25

• hydrogenolysis of 5a (Scheme 1). The reaction mechanism is suggested to follow a ketal deprotection sequence to arrive at the 4-piperidone derivative, which is protonated and reacts with the aromatic ring to afford the six member heterocycle. Deprotonation restores the aromatic ring and subsequent elimination of

Hydrogenation of aromatic ketones, aldehydes, and epoxides with hydrogen and Pd(0)EnCat™ 30NP

• Steven V. Ley,
• Angus J. P. Stewart-Liddon,
• David Pears,
• Remedios H. Perni and
• Kevin Treacher

Beilstein J. Org. Chem. 2006, 2, No. 15, doi:10.1186/1860-5397-2-15

• that different side reactions can take place like aromatic ring hydrogenation, as well as hydrogenolysis of the produced alcohol to the hydrocarbon derivative. [5][6] Some of these problems have been circumvented by adding ethylenediamine, [7] although this can make isolation of the product and

• University described the selective reduction of electron deficient and neutral aryl ketones to benzylic alcohols using Pd(0)EnCat™ 30NP as catalyst and a mixture of HCOOH/Et3N as the source of hydrogen [16]. Under these conditions they also achieved the chemoselective hydrogenolysis of aryl epoxides [17

• were obtained. The results are summarized in Table 2. trans-Stilbene oxide was chosen as a model for the hydrogenolysis of aromatic epoxides. The effect of different heterogeneous palladium catalysts and their propensity to over-reduce the benzylic alcohol generated after hydrogenolysis of the epoxide