Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

Concise total synthesis of two marine natural nucleosides: trachycladines A and B

• Haixin Ding,
• Wei Li,
• Zhizhong Ruan,
• Ruchun Yang,
• Zhijie Mao,
• Qiang Xiao and
• Jun Wu

Beilstein J. Org. Chem. 2014, 10, 1681–1685, doi:10.3762/bjoc.10.176

• environment of 2-OH the benzoylation with benzoyl chloride required an extended reaction time (48 h) and 2 equiv DMAP as base and catalyst. At last, the 1-O-methyl group was transformed to 1-O-acetate glycosylation acceptor 4 as an anomeric mixture (α:β = 2:3) in 84% yield. Therefore, the key intermediate 4

Stereoselective synthesis of carbocyclic analogues of the nucleoside Q precursor (PreQ₀)

• Sabin Llona-Minguez and
• Simon P. Mackay

Beilstein J. Org. Chem. 2014, 10, 1333–1338, doi:10.3762/bjoc.10.135

• following syn-dihydroxylation. Using the Upjohn conditions previously described we obtained the desired triol 18 in good yield and excellent diastereoselectivity (>99% by 1H NMR after column chromatography) [30]. Tri-benzoate 19 was subsequently obtained in good yield using the standard benzoylation

Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative

• Bernd Schmidt and
• Sylvia Hauke

Beilstein J. Org. Chem. 2014, 10, 1023–1031, doi:10.3762/bjoc.10.102

• benzoylation in pyridine resulted exclusively in the formation of furan 10 (Table 2, entry 1). We reasoned that pyridine initiates an E/Z-isomerization of the enal through nucleophilic attack at the β-position, followed by lactol formation, benzoylation of the lactol and finally elimination of benzoic acid

• better results were obtained with two different phosphine free catalysts comprising a hemilabile alkoxy substituted benzylidene ligand, even at only moderately elevated temperatures. The acrolein cross metathesis product can be converted into the 4-benzoate of L-amicetose via benzoylation, Pd-catalyzed

Synthesis of a derivative of α-D-Glcp(1->2)-D-Galf suitable for further glycosylation and of α-D-Glcp(1->2)-D-Gal, a disaccharide fragment obtained from varianose

• Carla Marino,
• Carlos Lima,
• Karina Mariño and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2012, 8, 2142–2148, doi:10.3762/bjoc.8.241

• α-D-Glcp unit in the HO-2 would hinder the proper diisoamylborane complexation. In order to relieve the conformational strain we prepared derivative 7 by deisopropylidenation followed by benzoylation of 5. Diisoamylborane reduction of 7 was more efficient and afforded 8 in 76% yield after 72 h of

• 100.4 and 99.3 for C-1 of the β and α-anomers, respectively. Derivative 8 is ready to be activated by the trichloroacetimidate method, for the synthesis of larger oligosaccharides. Conventional de-O-benzoylation and subsequent hydrogenolysis of 8 afforded disaccharide 1 in good yield (Scheme 1). The NMR

Enantioselective total synthesis of (R)-(−)-complanine

• Krystal A. D. Kamanos and
• Jonathan M. Withey

Beilstein J. Org. Chem. 2012, 8, 1695–1699, doi:10.3762/bjoc.8.192

• ). Although a number of acyloxylations have been reported, the direct catalytic asymmetric acyloxylation of aldehydes has only been recently realized [6][7]. Thus, the asymmetric benzoylation of aldehydes, according to the method of Tomkinson [7], was attempted. Utilizing benzoyl peroxide in the presence of

• MacMillan imidazolidinone (5R)-2,2,3-trimethyl-5-benzyl-4-imidazolidinone [8] with 4-nitrobenzoic acid as cocatalyst, all efforts to effect benzoylation of 3, yielding 5, were unsuccessful, and this route was ultimately abandoned as attention turned to more conventional α-oxygenation strategies and a

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• after benzoylation. Subsequent treatment of 11 with a second amount of Zn and LiCl (1.4 equiv) provides a new intermediate zinc reagent within 10 min, which after allylation provides the 2,5-disubstituted thiophene 12 in 87% yield (Scheme 3) [6]. The insertion reaction proceeds best with aryl and

• ketone are readily tolerated. Thus, the Boc-substituted benzophenone 130 reacts with TMP2Mg·2LiCl (1.1 equiv, −20 °C, 4 h) providing the expected aryl magnesium amide 131, which after a copper-mediated benzoylation leads to the 1,2,3-trisubstituted diketone 132 in 72% yield. This reagent allows a smooth

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• Glycosidation of 8-azidooctan-1-ol (Supporting Information File 2) using glycosyl bromide 11 [36] in the presence of AgOTf, and debenzoylation of the crude product gave 12 in 81% yield over 2 steps (Scheme 2). Regioselective silylation of the primary alcohol of 12 with TPSCl followed by benzoylation of the

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

• oxidation [45] of the ketone followed by reduction with NaBH4, afforded dihydroxy camphor derivative 67. Periodic acid cleavage of the resulting vicinal diol and NaBH4 reduction in situ gave diol 68. Selective benzoylation of the less hindered alcohol and PCC oxidation led to compound 70. Six derivatives of