Ring contraction and ring expansion reactions in terpenoid biosynthesis and their application to total synthesis

• Nicolas Kratena,
• Nicolas Heinzig and
• Peter Gärtner

Beilstein J. Org. Chem. 2026, 22, 289–343, doi:10.3762/bjoc.22.21

• 4-membered ring (see Scheme 23B). Finally, acetal formation on the novel carbaldehyde furnished the structure of pepluacetal (89). An interesting example for both the ring expansion and contraction of benzene rings in nature was unveiled during investigations into the biosynthesis of xenovulene A

Recent advancements in the synthesis of Veratrum alkaloids

• Morwenna Mögel,
• David Berger and
• Philipp Heretsch

Beilstein J. Org. Chem. 2025, 21, 2657–2693, doi:10.3762/bjoc.21.206

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

Synthesis of polycyclic aromatic quinones by continuous flow electrochemical oxidation: anodic methoxylation of polycyclic aromatic phenols (PAPs)

• Hiwot M. Tiruye,
• Solon Economopoulos and
• Kåre B. Jørgensen

Beilstein J. Org. Chem. 2024, 20, 1746–1757, doi:10.3762/bjoc.20.153

• estitmation of the HOMO/LUMO energies to shed more light on this transformation. The easy separation of the supporting electrolyte from the product will allow recycling and makes this a green transformation. Keywords: acetal formation; cyclic voltammetry; flow electrochemistry; green oxidation; polycyclic

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• . Acetal formation, reduction of the amide function and deprotection completed synthesis of (−)-hygrine (S)-61. To synthesize (−)-hygroline (2S,2'S)-62 and (−)-pseudohygroline (2S,2'R)-62 the carbonyl group in (S)-66 was reduced and the diastereoisomeric alcohols (2S,2'S)-67 and (2S,2'R)-67 were separated

Latest development in the synthesis of ursodeoxycholic acid (UDCA): a critical review

• Fabio Tonin and
• Isabel W. C. E. Arends

Beilstein J. Org. Chem. 2018, 14, 470–483, doi:10.3762/bjoc.14.33

• mechanism for this step is analogous to the mechanism for ketal or acetal formation except sulphur replaces oxygen as the nucleophile attacking the carbonyl group. In a second step, the dithioketal is reduced to the corresponding methylene compound by hydrogenolysis in presence of Raney Nickel (actually

Solution-phase automated synthesis of an α-amino aldehyde as a versatile intermediate

• Hisashi Masui,
• Sae Yosugi,
• Shinichiro Fuse and
• Takashi Takahashi

Beilstein J. Org. Chem. 2017, 13, 106–110, doi:10.3762/bjoc.13.13

• -8503, Japan 10.3762/bjoc.13.13 Abstract A solution-phase automated synthesis of the versatile synthetic intermediate, Garner’s aldehyde, was demonstrated. tert-Butoxycarbonyl (Boc) protection, acetal formation, and reduction of the ester to the corresponding aldehyde were performed utilizing our

• originally developed automated synthesizer, ChemKonzert. The developed procedure was also useful for the synthesis of Garner’s aldehyde analogues possessing fluorenylmethyloxycarbonyl (Fmoc) or benzyloxycarbonyl (Cbz) protection. Keywords: acetal formation; amino acid; automated synthesis; Garner’s aldehyde

• manually concentrated in vacuo. The obtained residue was purified manually using silica gel column chromatography. Carbamate 2a was obtained in 82% yield. Acetal formation was also demonstrated using ChemKonzert. A solution of substrate 2a in dichloromethane was stirred at 25 °C in the reaction vessel (RF1

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• ’-oxoaverantin (101) into averufin (102) by intramolecular acetal formation [87]. To date, it is not clear, how exactly the OAVN cyclase participates in this process [88]. Interestingly, the OAVN cyclase operates cofactor-free, although it contains a NAD(P)+-binding Rossman fold. Furthermore, this enzyme is also

Synthesis and biological evaluation of a novel MUC1 glycopeptide conjugate vaccine candidate comprising a 4’-deoxy-4’-fluoro-Thomsen–Friedenreich epitope

• Manuel Johannes,
• Maximilian Reindl,
• Bastian Gerlitzki,
• Edgar Schmitt and
• Anja Hoffmann-Röder

Beilstein J. Org. Chem. 2015, 11, 155–161, doi:10.3762/bjoc.11.15

• ’-fluoro-TF SPPS building block 11 started by conversion of peracetylated D-glucose 1 into β-thio-glycoside 2 [45][46] under Lewis acid catalysis in 81% yield (Scheme 1). Subsequent Zemplén deacetylation [47], followed by 4,6-benzylidene acetal formation and acetylation provided fully protected precursor 3

Synthesis of rigid p-terphenyl-linked carbohydrate mimetics

• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 1749–1758, doi:10.3762/bjoc.10.182

• °C; b) 1. THF, 2 h, −78 °C; 2. H2O, 1 h, −78 °C → rt. Synthesis of 1,2-oxazine 4 by acetal formation from 10. Conditions: a) 1-bromo-4-(dimethoxymethyl)benzene (10 equiv.), CAN, CH2Cl2, 3 d, rt. Synthesis of bicyclic ketone 11 by Lewis acid-induced rearrangement and reduction to alcohols 12a and 12b

Re₂O₇-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles

• Wantanee Sittiwong,
• Michael W. Richardson,
• Charles E. Schiaffo,
• Thomas J. Fisher and
• Patrick H. Dussault

Beilstein J. Org. Chem. 2013, 9, 1526–1532, doi:10.3762/bjoc.9.174

• higher yield of acetal. The Re2O7-promoted reactions were subsequently found to proceed efficiently at only 1% catalyst loading. Neither catalyst allowed etherification with a tertiary alcohol. Acetal formation As illustrated in Table 2, we next investigated acetalization of tetrahydrofuranol 3

• oxybisacetals (Table 3). As will be described later, these apparent byproducts proved to be competent substrates for acetal formation. We next attempted to maximize the yield of acetal based upon alcohol (Table 4). Good yields were obtained at a 1:1 ratio of alcohol to hemiacetal and yields did not vary

Short synthesis of the common trisaccharide core of kankanose and kankanoside isolated from Cistanche tubulosa

• Goutam Guchhait and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2013, 9, 705–709, doi:10.3762/bjoc.9.80

• the presence of borontrifluoride diethyl etherate furnished 2-phenylethyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside (2) in 84% yield [10]. Saponification of compound 2 by using 0.1 M sodium methoxide in methanol followed by benzylidene acetal formation by using benzaldehyde dimethylacetal in the

Branching out at C-2 of septanosides. Synthesis of 2-deoxy-2-C-alkyl/aryl septanosides from a bromo-oxepine

• Supriya Dey and
• Narayanaswamy Jayaraman

Beilstein J. Org. Chem. 2012, 8, 522–527, doi:10.3762/bjoc.8.59

• been explored in many instances, for example, (i) hemiacetal or acetal formation from a linear precursor containing aldehyde and an appropriately positioned hydroxyl group [4][5][6][7][8]; (ii) Knoevenagel-type condensation of sugar aldehyde with active methylene compounds [9][10]; (iii) ring-closing

Acceptor-influenced and donor-tuned base-promoted glycosylation

• Stephan Boettcher,
• Martin Matwiejuk and
• Joachim Thiem

Beilstein J. Org. Chem. 2012, 8, 413–420, doi:10.3762/bjoc.8.46

• -glycopyranoside acceptor 6 started with benzylidenation [4] of 19, followed by monobenzylation via intermediate stannylidene acetal formation [6] and subsequent cleavage of the benzylidene group [4]. Formation of the perbenzylated α-fucopyranosyl chloride was achieved according to [2]. Starting with peracetylated

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• acetals from dichlorodiphenylsilane. Attempted Pauson-Khand reaction of allylpropargyldiphenylsilyl acetal. Proposed diisopropylsilyl acetal formation. Attempted allylpropargyldiisopropylsilyl acetal formation. Attempted allylpropargyldiisopropylsilyl acetal formation. Preparation of silicon-tethered