Exploration of an epoxidation–ring-opening strategy for the synthesis of lyconadin A and discovery of an unexpected Payne rearrangement

• Brad M. Loertscher,
• Yu Zhang and
• Steven L. Castle

Beilstein J. Org. Chem. 2013, 9, 1179–1184, doi:10.3762/bjoc.9.132

• addition to its interesting bioactivity, lyconadin A presents a significant synthetic challenge by virtue of its unique pentacyclic skeleton, which contains six stereocenters and a pyridone ring. It is therefore not surprising that 1 has attracted the attention of the organic synthesis community. The first

Cascade radical reaction of substrates with a carbon–carbon triple bond as a radical acceptor

• Hideto Miyabe,
• Ryuta Asada and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2013, 9, 1148–1155, doi:10.3762/bjoc.9.128

• bulky substituent R1 leading to the dissociation of the chiral Lewis acid. In these studies, the absolute configuration at newly generated stereocenters has been not determined. We recently reported in detail the cascade addition–cyclization–trapping reaction of substrates with carbon–carbon double

• conditions, an outstanding level of enantioselectivity was observed on employing the bulky tert-butyl iodide as a radical precursor (Table 1, entry 14). A good yield of the product 9Bd was obtained with 92% ee and high Z-selectivity. The absolute configuration at the newly generated stereocenters of 9Aa–Bd

• for preparing functionalized cyclic compounds with multiple stereocenters. These studies offer opportunities for further exploration of fascinating possibilities in the realm of cascade radical reactions. Cascade bond formation based on radical reactions. Our method for controlling the geometry of

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

• Toshiki Tabuchi,
• Daisuke Urabe and
• Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

• (+)-2 from racemic 6 generated the unnecessary antipode. Therefore, development of an alternative asymmetric route to 1 was planned to further improve the overall practicality. Here we report an asymmetric Diels–Alder reaction for simultaneous installation of the C1- and C5-stereocenters using the

• expected to stereoselectively introduce the C1, C5 and C12 stereocenters to afford bicyclo[3.2.2]nonene 8. The C11-aldehyde of 8 was then to be utilized as a handle for the ring expansion to access 1. To the best of our knowledge, construction of the two quaternary carbons by the intermolecular Diels–Alder

The diketopiperazine-fused tetrahydro-β-carboline scaffold as a model peptidomimetic with an unusual α-turn secondary structure

• Francesco Airaghi,
• Andrea Fiorati,
• Giordano Lesma,
• Manuele Musolino,
• Alessandro Sacchetti and
• Alessandra Silvani

Beilstein J. Org. Chem. 2013, 9, 147–154, doi:10.3762/bjoc.9.17

• of the THBC-DKP scaffold also in solution, compound 6 was converted into the N-methyl carboxyamide derivative 1a, by a two-step procedure (0.5 M LiOH, 0 °C, then MeNH2, TBTU, DIPEA), which was carefully conducted in order to avoid the easy epimerization of the C3 and C12a stereocenters. Spin-system

A new approach toward the total synthesis of (+)-batzellaside B

• Jolanta Wierzejska,
• Shin-ichi Motogoe,
• Yuto Makino,
• Tetsuya Sengoku,
• Masaki Takahashi and
• Hidemi Yoda

Beilstein J. Org. Chem. 2012, 8, 1831–1838, doi:10.3762/bjoc.8.210

• prepared through a separate route (Scheme 1) [19]. In this approach involving nucleophilic cyclization of acyclic aldehyde in situ generated from olefin 2 for constructing the piperidine ring system, proper synthetic manipulation of the three inherent stereocenters contained in the chiral source was a key

Asymmetric desymmetrization of meso-diols by C₂-symmetric chiral 4-pyrrolidinopyridines

• Hartmut Schedel,
• Keizo Kan,
• Yoshihiro Ueda,
• Kenji Mishiro,
• Keisuke Yoshida,
• Takumi Furuta and
• Takeo Kawabata

Beilstein J. Org. Chem. 2012, 8, 1778–1787, doi:10.3762/bjoc.8.203

• functionality and chirality of catalyst side chains do not affect the absolute configuration of the monoacylate obtained by the asymmetric desymmetrization while they influence the extent of the enantioselectivity. Accordingly, the configuration of the stereocenters in C(2) and C(5) position bearing the amide

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• , which afforded versatile succinimide-containing benzothiopyrans 43 with the generation of three stereocenters in one single operation (Scheme 22). The method provides a general approach to the preparation of a range of substituted benzothiopyrans containing three stereocenters, with high enantiomeric

• acid additive (Scheme 23). Avoiding the dehydration step, it is possible by this protocol to obtain thiochromans 45 bearing three contiguous stereocenters and a tertiary aldol structural motif with excellent enantioselectivities (96–99% ee) and yields (71–98%), and with good diastereocontrol (10:1 to

• (up to 98% de). Later on the same group [71] developed another hydrogen-bond-mediated catalysis for the synthesis of tetrasubstituted thiochromans having three continuous stereocenters 49 following domino thio-Michael–Knoevenagel reaction between 2-mercaptobenzaldehydes 34 and benzylidenemalonates 48

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• (MBH) carbonates with maleimides, which can efficiently construct functionalized cyclopentenes bearing three contiguous stereocenters in moderate to excellent yields and excellent diastereo- and enantioselectivities. A plausible mechanism has been also proposed on the basis of control experiments and

• + 2] annulation of MBH carbonates with maleimides, which can efficiently construct functionalized cyclopentene derivatives bearing three contiguous stereocenters in moderate to excellent yields along with excellent diastereo- and enantioselectivities. Results and Discussion In our previous work, it

• product 4c containing five stereocenters was produced in 69% yield and good diastereoselectivity on the basis of NMR spectroscopic data (dr = 20:1, see Supporting Information File 1). Conclusion In conclusion, we have developed a novel multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• stereocenters, including a quaternary carbon. As in the previous examples, the gold-catalyzed cyclization benefits strongly from a stabilizing substituent at C2 to direct the 6-endo mode of cyclization. Subsequent to the success of the gold-catalyzed cycloisomerization in trapping the developing carbocation

High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• dinuclear gold(I) complex 36 [44] gave the same result (Figure 3). When the catalyst was changed to platinum(II) chloride in acetone, a complex mixture of inseparable products was obtained. Since the two diastereoisomers 28a and 28b with the propargylic stereocenters were separable, we investigated the gold

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• , the complexity of the products is considerably increased with respect to that of the reactants, as a new ring and up to four new stereocenters are formed. The first “classical” [2π + 2π] photocycloaddition of benzene was described by Angus and Bryce-Smith in 1959 [7]. However, Ayer, Bradford and Büchi

• stereocenters in a single step from planar achiral starting materials. If substituents are added to the arene and the complexity of the olefin is increased, a great diversity of products can be created. However, not all of these products are accessible via such a photocycloaddition, as many possibilities can be

Brønsted acid-promoted azide–olefin [3 + 2] cycloadditions for the preparation of contiguous aminopolyols: The importance of disiloxane ring size to a diastereoselective, bidirectional approach to zwittermicin A

• Hubert Muchalski,
• Ki Bum Hong and
• Jeffrey N. Johnston

Beilstein J. Org. Chem. 2010, 6, 1206–1210, doi:10.3762/bjoc.6.138

• particularly intrigued by the possibility of a substrate controlled anti-diastereoselective azide–olefin reaction performed in a bidirectional fashion [13][14] to establish the requisite stereocenters of the C9–C15 C2 symmetric core of the natural product [11] as outlined in Scheme 1. Diastereoselective

Novel tetracyclic structures from the synthesis of thiolactone-isatin hybrids

• Renate Hazel Hans,
• Hong Su and
• Kelly Chibale

Beilstein J. Org. Chem. 2010, 6, No. 78, doi:10.3762/bjoc.6.78

• in the tetracycles 4 was further sparked by the ease and simplicity of their preparation, and the novelty of their architecture as revealed by single X-ray crystal structure analysis. Attractive structural features of 4 include two vicinal quaternary stereocenters and a complex, bicyclic ring system

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• stereocenters (Scheme 10) [23]. Sulfonyl-substituted ynamide 22 has also been investigated in carbocupration and copper-catalyzed carbomagnesiation reactions (Scheme 11) [22]. Irrespective of the conditions, the carbometalation reaction on sulfonyl-substituted ynamide 22 is slower than that with ynamide 17. In

A short stereoselective synthesis of (+)-(6R,2′S)-cryptocaryalactone via ring- closing metathesis

• Palakodety Radha Krishna,
• Krishnarao Lopinti and
• K. L. N. Reddy

Beilstein J. Org. Chem. 2009, 5, No. 14, doi:10.3762/bjoc.5.14

• wherein a chiral 2,3-epoxy alcohol was the starting material and Sharpless asymmetric epoxidation and Carreira asymmetric alkynylation were used as key steps for generating unambiguous assigned stereocenters. More importantly, the Grubbs’ ring-closing metathesis protocol was applied to construct the final

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

• (2S)-10,2-camphorsultam. The key oxidative cyclization reaction, conducted under phase-transfer conditions, introduced the C15, C16, C19, and C20 stereocenters present in cis-solamin in one step, then the auxiliary was best removed from 79 by reduction using NaBH4. The resulting diol was taken forward

• acetogenins contains six oxygenated stereocenters, and much of the synthetic work on the family has been focused in that direction. The first successful approach was recorded in 1991 by Hoye’s group who employed a two-directional inside-out epoxide cascade sequence to prepare a core enantiomer of uvaricin [66