bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of 22‐Cupriosteroids, a New Route to Steroids Possessing Oxygenated Side Chains
Authors: Scherlitz‐Hofmann Ina , Bößneck Ulrich , Schönecker Bruno 
Published: June 2010

AbstractA new method for the synthesis of steroids with oxygenated side chains starting from C22 steroids is described. Rieke copper, obtained by reduction of lithium 2‐thienylcyanocuprate 4 with lithium naphthalenide at −78°C or −100°C, reacts with the 22‐bromosteroids 1a, 2, 14 to afford the corresponding cupriosteroids. In addition to the metalation a very smooth retro Diels‐Alder reaction takes place in the case of 14 at the B ring. The steroid‐copper compounds react with (±)‐1,2‐epoxypropane to furnish epimeric mixtures of the 24‐hydroxysteroids 6, 8 and 15 in good yields. The procedure described is useful for a short synthesis of (24R)‐cholesta‐5,7‐diene‐3β,24,25‐triol (17, as 3‐silyl ether), the provitamin of the main metabolite (24R)‐24,25‐dihydroxyvitamin D3, using 14, Rieke copper and the highly functionalized chiral building block 10/n‐butyllithium.
New Compounds from 6,7‐Dihydrobenzo[c]thiophen‐4(5H)‐ones.
Authors: Prim Damien , Joseph Delphine , Kirsch Gilbert 
Published: June 2010

AbstractThe reactivity of the ketone moiety in 6,7‐dihydrobenzo[c]‐thiophen‐4(5H)‐ones 1 was used to generate new benzo[c]‐thiophene derivatives. The behaviour of the ketones under Vilsmeier‐Haack‐Arnold conditions was studied. Generally, the reactivity of the ketone moiety is shown to be dependent on the substituents of the thiophene ring.
On the Reaction of Nitrilium Salts with Secondary Carboxamides
Authors: Hitzler Martin G. , Lutz Martin , Shrestha‐Dawadi Prativa Bade , Jochims Johannes C. 
Published: June 2010

AbstractNitrilium salts 1, the first products of the Beckmann rearrangement of oximes, react with secondary amides 2, the final products of this rearrangement, to afford mixtures of up to four different N‐acylamidinium salts 3–6 (mechanism Scheme 4). The ratio 3/4/5/6 depends on the configuration of 2, the substituents of 1 and 2, the reaction temperature and the concentrations of the reactants. With tertiary amides nitrilium salts give only one N‐acylamidinium salt, the formation of which is also explained by the mechanism of Scheme 4. An X‐ray structural analysis in reported for the product obtained from 2‐pyridone and N‐isopropylbenzonitrilium hexachloroantimonate. First cyclic nitrilium salts (1d, k, w) were prepared.
Synthesis of Protected 4‐Deoxyaklanonic Acid via Naphthalene‐substituted Oligoketides
Authors: Krohn Karsten , Schäfer Gisbert 
Published: June 2010

AbstractKetide side chains (C4) were attached to the naphthoquinone 3 by reaction with the dienes 4 or 14 followed by Baker‐Venkataraman rearrangement of esters 8 and 17 to attach the second protected β‐diketo side chain. Linear anellations of the corresponding naphthoquinone precursors 9 and 17 to the 4‐deoxyaklanonic acids 10 and 18a, respectively, were effected in a base‐catalyzed cascade of reactions (e.g. only three operations from 3 to 18a).
Donor‐substituted oligothiophenes, 1 synthesis and properties of a series of methylthio oligothiophenes
Authors: Bäerle Peter , Götz Günther , Synowczyk Andreas , Heinze Jürgen 
Published: June 2010

AbstractA homologous series of donor‐substituted oligothiophenes 7–9 bearing methylthio groups in the „outer”︁ β‐positions were synthesized up to a quaterthiophene. The physical properties are dependent on the chain length of the conjugated system. The compounds exhibit biological activities. Due to the substitution pattern, even the longer oligomers exhibit good film‐forming properties and could be electropolymerized to the corresponding donor‐substituted polythiophenes P7–P9 with a stereoregular structure. The electronic properties were found to be dominated by the donor strength of the substituents.
A Simple Route to New Macrocyclic Ligand Skeletons: Syntheses and Crystal Structures of Poly(ethoxycarbonyl)[3n]phanes
Authors: Meiners Christian , Vögtle Fritz , Nieger Martin 
Published: June 2010

AbstractNew types of macrocyclic complexing agent precursors with [3n]phane molecular skeletons were synthesized by reaction of 1,3‐bis(bromomethyl)arenes with sodium ethyl malonates. After chromatographic separation, the eighteen‐membered trimethoxy[33]metacyclophane II1a together with the twentyfour‐membered tetramethoxy[34]metacyclophane II2a and the twentyfour‐membered [34](2,6)pyridinophane I2a could be isolated as crystalline compounds. The crystal structures of I2a, II2a, and III1a were determined by single‐crystal X‐ray structure analyses. The presented syntheses of the proposed molecular skeletons of metacyclophane type II and pyridinophane type I provide a facile route to substituted macrocycles which can be easily converted into polyacids with manifold substitution patterns.
The Cubane Cage – a Sensible Probe for Substituent Effects on a Four‐membered Ring
Authors: Irngartinger Hermann , Strack Stefan , Gredel Frank 
Published: June 2010

AbstractThe crystals of methyl 4‐fluoro‐1‐cubanecarboxylate (1), methyl 4‐chloro‐1‐cubanecarboxylate (2) and methyl cubanecarboxylate (5) are isomorphous to each other as are the crystals of methyl 4‐bromo‐1‐cubanecarboxylate (3) and methyl 4‐iodo‐1‐cubanecarboxylate (4). As a result of the space groups P21/m and Pnma, respectively, all molecules lie in a crystallographic mirror plane. Therefore, the methoxycarbonyl group is exactly planar, and the carbonyl fragment is in an eclipsed position to the cubane skeletal bond C2–C7. The electronic effects of the halogen atoms, in particular fluorine and chlorine, give rise to a shortening of the vicinal skeletal bonds. In contrast, the methoxycarbonyl groups causes a lengthening of the vicinal skeletal bonds C2–C6 and C2–C6A which are not in an eclipsed conformation. Ab initio calculations at the 6–31G level of compounds 1, 2, and 5 confirm the experimental results.
Ring Closure of 4‐Azido‐3‐formyl‐(or Acetyl‐)2‐pyridones to Isoxazolo[4,3‐c]pyridones
Authors: Khattab Ahmed F. 
Published: June 2010

AbstractAzidation of the chlor aldehyde 2, which was obtained from the 4‐hydroxy‐2‐pyridone 1, afforded the ring‐closed isoxazolopyridone 3. Thermolysis of the 3‐acetyl‐4‐azido‐2‐pyridone 8, which was obtained from the corresponding 4‐tosyloxy derivative 7, afforded isoxazolopyridine 9. Amination of the chloro aldehyde 2 yielded the pyrido[4,3‐b]quinoline 11 instead of the 4‐chloroazomethine 10.
Verbotene Reaktionen, II Die disrotative Cyclobuten‐Ringöffnung
Authors: Roth Wolfgang R. , Rekowski Volker , Börner Sabine , Quast Michael 
Published: June 2010

Forbidden Reactions, II. – The Disrotatory Cyclobutene RingopeningThe energy profiles for the con‐ and disrotatory opening of benzocyclobutene, methylenecyclobutene, and cyclobutene derivatives were established by NO and oxygen trapping. The enthalpy for the transition states for the forbidden reactions proved to be identical with the heat of formation of the orthogonal diradicals derived by geometrical isomerization of the dienes formed in these reactions. These diradicals describe very well the activation barriers observed for the disrotatory opening of bicyclic cyclobutenes ([3.2.0] and [2.2.0] systems), but not for bicyclo[2.1.0]pent‐2‐ene, indicating here a truly forbidden reaction.
Deamination Reactions, 58. Stereoselectivity of 2‐Methyl‐2‐norpinyl Cations
Authors: Herrmann Roland , Kirmse Wolfgang 
Published: June 2010

AbstractOptically active (1S)‐1‐methylbicyclo[2.2.1]heptan‐2‐one (25) was prepared by starting from (1R)‐bicyclo[2.2.1]heptan‐2‐one (21). Photolysis of the tosylhydrazone 8 of 25 generates, in part, 1‐methylbicyclo[2.2.1]heptane‐endo‐2‐diazonium ions (10) from which 1‐methylbicyclo[2.2.1]heptan‐endo‐2‐ol (14) and 2‐methylbicyclo[3.1.1]heptan‐2‐ol (16) arise. The ee of both products (42–45%) was found to agree within experimental error. These data point to the bridged 2‐methyl‐2‐norpinyl cation (13) as the most stable structure. Racemization of 13 via the open 2‐methyl‐2‐norpinyl cation (17) as the transition state competes with nucleophilic capture.
A Convenient Synthesis of (4R,7Z,11Z)‐(‐)‐4‐Methylheptadeca‐7,11‐dienal and (4R,7Z,11Z)‐4‐Methylheptadeca‐7,11‐dienoic Acid
Authors: Sharma Anubha , Chattopadhyay Subrata 
Published: June 2010

AbstractA synthesis of the title aldehyde 1 and acid 2, the (R) enantiomers of the antifungal and antibacterial principles of Sporothrix species, was developed. Alkylation of the alkynol derivative 6 with (S)‐citronellyl bromide (5), depyranylation, cis hydrogenation, PCC oxidation, and Z‐selective Wittig reaction with hexylidenephosphorane gave the hydrocarbon 11. Its regioselective epoxidation and cleavage of the epoxide with HlO4 affords (R)‐1 which was oxidized to (R)‐2.
Studies with Altrose Derivatives – A Convenient Approach to α‐Linked Digitoxosides
Authors: Miethchen Ralf , Rentsch Daniel 
Published: June 2010

AbstractThe 2‐O‐(cyclohexylcarbamoyl)‐3,4‐O‐(2,2,2‐trichloroethylidene)‐protected α‐altropyranosyl fluorides 1, 7, and 11 were used as starting materials for intra‐ and intermolecular glycosylations in the presence of BF3. Because of the effective neighbouring group participation of the carbamoyl moieties, the corresponding trans‐glycosides 2, 4, 6, 12, and 14 can be stereoselectively prepared from 1 and 11, respectively, in good yields. In the case of the 6‐O‐formyl derivative 7 the intramolecular glycosylation to 1,6‐anhydro‐2‐O‐(cyclohexylcarbamoyl)‐3,4‐O‐(2,2,2‐trichloroethylidene)‐β‐D‐altropyranoside (8) is possible, when no other competing nucleophiles are present. Furthermore, the deoxygenation of the altrose moiety of 6‐O‐[6‐deoxy‐3,4‐O‐(2,2,2‐trichloroethylidene)‐α‐l‐altropyranosyl]‐1,2: 3,4‐di‐O‐isopropylidene‐α‐D‐galactopyranose (15) in 2‐position and the hydrogenolysis of the trichloroethylidene acetal protecting group were simultaneously realised. 6‐O‐(2,6‐Dideoxy‐3,4‐O‐ethylidene‐α‐l‐ribo‐hexopyranosyl)‐1,2:3,4‐di‐O‐isopropylidene‐α‐D‐galactopyranose (16) was obtained by reduction of the intermediately prepared 2‐xanthate of 15 with Bu3SnH/AIBN.
Azo Bridges from Azines, XIX. Intramolecular \documentclass{article}\pagestyle{empty}\begin{document}$ \left[ {\sigma _{\rm s}^2 + \pi _{\rm s}^2 } \right] $\end{document} Photocycloaddition Reaction of Parallel Three‐Membered Rings with Azo Groups
Authors: Hünig Siegfried , Schmitt Michael 
Published: June 2010

Abstract[3 + 2] Photocycloaddition reaction of three‐membered rings with azo groups were accomplished for the first time by photochemically induced π,π* excitation of several systems of the general typeCEexemplified by1,3,5,7,10,13, and17. Intramolecular reaction of the parallel arranged functional groups yields cage compoundsFH(2,4,6,8,11,14, and18) in a [σs2+ πs2] process, SystemsCEare inert on n,π* excitation in aprotic solvents. In methanol or better 2‐propanol, however, the azo groups are reduced from their triplet states. The resulting hydrazino groups, also available by catalytic hydrogenation, open the aziridine rings of7,10, and13as well as the oxirane ring of17by nucleophilic attack, producing the half cages9,12, and19.
Azo Bridges from Azines, XX.
Authors: Brand Uwe , Hünig Siegfried 
Published: June 2010

AbstractIntroduction of a cyano group into the olefinic bridge of 10 (type A) leads to the formation of 16 (type C) in high yield. To obtain 16 first 10 is transformed into isoxazoline 11 which is opened to hydroxy nitrile 12 (type B) from which after brosylation (15) 16 is isolated. Reduction of the azo bridge in 15 affords half cage 13. Smooth oxidation of 12 yields oxo nitrile 19, from which under basic conditions another half cage (18) results. Unexpectedly, on heating with triethylamine 19 undergoes complete rearrangement of the bridges, 21 being formed on release of strain. The course of this reaction which has to pass through a cage with a diazetidine moiety is discussed.
Biologically Active Glycosides from Asteroidea, XXXIV. Isolation and Structure of Cerebrosides from the Starfish Stellaster equestris
Authors: Higuchi Ryuichi , Harano Yoichiro , Mitsuyuki Mika , Isobe Ryuichi , Yamada Koji , Miyamoto Tomofumi , Komori Tetsuya 
Published: June 2010

Biologically Active Glycosides from Asteroidea, XXXIV. – Isolation and Structure of Cerebrosides from the Starfish Stellaster equestrismagnified image
O‐Glycoside Synthesis under Neutral Conditions in Concentrated Solutions of LiClO4 in Organic Solvents Employing Benzyl‐Protected Glycosyl Donors
Authors: Böhm Gerd , Waldmann Herbert 
Published: June 2010

AbstractThe benzyl‐protected glucosyl trichloroacetimidates, phosphates, and halides 1 are activated under neutral conditions and without the addition of any further promoter in 1 M solutions of LiClO4 in ether, CH2Cl2, CHCl3, or CH3CN and react under these conditions with the model alcohols 3 to give the glycosides 4 in moderate yields. If the α‐imidate 1a or the β‐phosphate 1d is used as glycosyl donor, in the majority of the cases 1:1 mixtures of the anomers are obtained. In contrast, the β‐imidate 1b gives a distinct excess of the α‐glycosides and if the α‐phosphate 1c is employed, the β‐anomers are formed preferentially. Whereas the glycosyl chloride 1f and the glycosyl bromide 1e are not the donors of choice under these conditions, from the β‐fluoride 1g the desired O‐glycosides are readily obtained. In 3–5 M solutions of LiClO4 in ether instead of the expected glycosides benzyl‐protected 1,6‐anhydroglucose 6 is formed and the imidazolylcarbonylactivated carbohydrate 1h reacts with the alcohols 3 to give the glycosyl carbonates 5. Whereas CH2Cl2 and CHCl3 do not influence the stereoselectivity of the glycosylations in ether or CH3CN, the solvent seems to participate in the steric control of the O‐glycoside formation.
Regioselectivity in SNH Reactions of Nitroquinolines with Chloromethyl Phenyl Sulfone
Authors: Grzegożek Maria , Woźniak Marian , van der Plas Henk C. 
Published: June 2010

Abstract3‐Nitro‐, 4‐nitro‐, 7‐nitro‐, 5,7‐dinitro‐, and 6,8‐dinitroquinoline react with the carbanion of chloromethyl phenyl sulfone to give products of substitution of hydrogen at positions 4, 3, 8, 6,8, and 5,7, respectively. The reactions are found by quantum chemical calculations to be controlled by the interactions of the HOMO of the nucleophile with the LUMO of the substrate. The σ adducts 4‐(methylsulfonylphenyl)‐3‐nitroquinoline and 3‐(methylsulfonylphenyl)‐4‐nitroquinoline are detected by 1H‐NMR spectroscopy. In addition, heats of formation of the intermediary σ adducts 2a–d, f, h, and i are calculated.
Inverse and Normal [4 + 2] Cycloadditions of a 4a,8a‐Methanophthalazine to Azirines and 1,2,4‐Triazoline‐3,5‐dione as Heterodienophiles
Authors: Laue Jörg , Seitz Gunther 
Published: June 2010

AbstractThe 4a,8a‐methanophthalazine 4 is a novel propellane containing an electron‐rich cyclohexadiene and an electron‐deficient diazadiene system within the same molecule. The highly strained azirines 6 and 9a–c, prepared from the corresponding vinyl azides 5 and 8a–c, undergo cycloaddition in situ to the diazadiene system of 4 to furnish the stable polycyclic azo compounds 7c and 10–12 which possesses exo configuration at the annulated aziridine. Attack apparently occurs from the less hindered face, anti to the methano bridge of 4 with high stereo‐ and site selectivity. The electron‐deficient 1,2,4‐triazoline‐3,5‐dione 13 reacts with the electron‐rich diene of the azo compound 12 to yield the anti‐anti bisadduct 14.
1,2:5,6‐Di‐O‐isopropylidene‐α‐D‐gulofuranose as a Chiral Auxiliary in the Diastereoselective C Methylation of Ester Enolates. The Influence of the Base on the Stereochemistry of Enolate Formation and Alkylation
Authors: Mulzer Johann , Hiersemann Martin , Buschmann Jürgen , Luger Peter 
Published: June 2010

AbstractThe C methylation of the carbohydrate‐derived O‐chiral esters 5a‐d to derivatives 8 proceeds with (R) selection of 1:1 to 10:1 and depends primarily on the base used for enolate generation. Lithium 2,2,6,6‐tetramethylpiperide (LTMP) shows the highest and lithium hexamethyldisilazanide (LHMDS) the lowest selection. These results are interpreted in terms of a “post‐enolization complex” involving the lithium amide base.
Syntheses, Structures, and Complexation Properties of Photoresponsive Crownophanes
Authors: Fürstner Alois , Seidel Günter , Kopiske Carsten , Krüger Carl , Mynott Richard 
Published: June 2010

AbstractA set of tethered bis‐benzophenone or ‐benzaldehyde derivatives was subjected to intramolecular McMurry reactions, thus affording hybrids with cyclophane and crown ether substructures (“crownophanes”). All macrocycles were formed in reasonable yields even at rather high concentrations. A comparative study showed that low‐valent titanium [Ti] exerts a strong template effect whereas alkali metal salts accumulating during its preparation have only little influence upon the preorganization of the substrates in a favorable podand‐like conformation. Ester linkages in the tethers turned out to be only partly compatible with the reaction conditions. Crystal structures of crownophanes 7, 8, and 12 are described. A 1H‐ and 13C‐NMR study on the complexation of Ag(+1) by 8 and 10 revealed that the endocyclic arene entities rather than the polyether chains are the major sites of interaction of the cation with its host.
Conformational Analysis of Benzoannulated Nine‐Membered Rings, 5. 1,2,6,7‐Tetrahydro‐4H‐3,5‐benzodioxonin
Authors: Rys Barbara , Szneler Edward , Duddeck Helmut 
Published: June 2010

AbstractTemperature‐dependent 1H‐ and 13C‐NMR spectra of the title compound are presented. Coalescence effects are discussed and assigned to two dynamic processes: (a) ring inversion of the nine‐membered ring, (b) racemization of the enantiomeric ground‐state conformations of the nine‐membered ring. The barriers are 52 and 35 kJ mol−1, respectively. The stability of the ground state conformation is discussed in terms of transannular hydrogen interactions and anomeric effects. An assignment of the proton signals in the groundstate conformation is proposed.
Synthesis of Sterically Fixed Podophyllotoxins
Authors: Laatsch Hartmut , Ernst Bernd Peter , Noltemeyer Mathias 
Published: June 2010

AbstractPodophyllotoxin and epi‐podophyllotoxin derivatives (1/2) with an unsaturated side chain at C‐5a were obtained by C‐alkylation of protected derivatives of 1. The azide 3a afforded 4 in quantitative yield at 80°C. With pyridine/acetyl chloride, the latter yielded the rigid epi‐podophyllotoxin derivative 7, whose structure was established by crystal structure analysis. All reported podophyllotoxin derivatives are less cytotoxic than podophyllotoxin (1a) itself.
Microwave‐Assisted Carbonyl Diels‐Alder and Carbonyl‐Ene Reactions Supported on Graphite
Authors: Garrigues Bernard , Laurent Régis , Laporte Christian , Laporterie André , Dubac Jacques 
Published: June 2010

Abstract“Dry” carbonyl Diels‐Alder and carbonyl‐ene reactions with microwaves and reactants supported on graphite were dramatically accelerated with respect to homogeneous conditions both involving classical or microwave heating. Although the reactions were carried out in an open reactor, a control of the evaporation of volatile reagents was possible, probably due to their retention or confinement by graphite.
Novel Dienes and Dienophiles, VI. On the Chemical Behavior of 2‐Ethynyl‐1,3‐butadiene
Authors: Hopf Henning , Jäger Helge , Ernst Ludger 
Published: June 2010

AbstractThe behavior of 2‐ethynyl‐1,3‐butadiene (1) as the diene component in Diels‐Alder additions has been studied using a selection of representative double and triple bond dienophiles. The latter include maleic anhydride (5a), diethyl fumarate (6), benzoquinone (7), methyl acrylate (11), juglone (20), 1‐methylcyclopropene (23), dimethyl acetylenedicarboxylate (26), propiolic aldehyde (32), 4‐phenyl‐1,2,4‐triazolin‐3,5‐dione (35) and diethyl azodicarboxylate (37). [2 + 4] Cycloadducts were formed in all cases in varying yields. The addition is accompained by thermal dimerization of 1 which leads to 1,4‐diethynyl‐4‐vinyl‐1‐cyclohexene (43) and 1,6‐diethynyl‐1,5‐cyclooctadiene (39). The mechanism of this dimerization is discussed. In a competition experiment towards maleic anhydride (5a), diene 1 was shown to be ca. five times less reactive than isoprene.
Syntheses of β‐Lactones, 6. One‐Step Synthesis of β‐Lactones by Aldolization of Ketones or Aldehydes with 1‐Acylbenzotriazoles
Authors: Wedler Christine , Kleiner Katharina , Kunath Annamarie , Schick Hans 
Published: June 2010

AbstractBenzotriazolides 1 of alkanoic acids with one hydrogen atom in α‐position to the carboxamide group can be deprotonated with lithium diisopropylamide or lithium hexamethyldisilazanide to amide enolates 2 which condense at −90 to −95°C with ketones or aldehydes 3 to afford benzotriazolides of O‐lithiated β‐hydroxylalkanoic acids 4. These reactive carboxamide derivatives cyclize with elimination of lithium benzotriazolide to the corresponding di‐ and trisubstituted β‐lactones. With regard to the formation of β‐monosubstituted β‐lactones from aldehydes the use of benzotriazolides as active carboxylic acid derivatives proved to be superior to the application of the corresponding phenyl esters. An α‐unsubstituted β‐lactone 6 was obtained from 1‐acetylbenzotriazole only with cyclohexanone. The other carbonyl compounds 3 did not provide the corresponding α‐unsubstituted β‐lactones 6.
Utilization of Industrial Waste Materials, 6. Utilization of Derivatives of the Bicyclic Proline Analog (all‐R)‐Octahydrocyclopenta[b]pyrrol‐2‐carboxylic Acid in the Stereoselective Synthesis
Authors: Wilken Jörg , Wallbaum Sabine , Saak Wolfgang , Haase Detlef , Pohl Siegfried , Martens Jürgen , Patkar Laxmikant N. , Dixit Arun N. , Chittari Pabba , Rajappa Srinivasachari 
Published: June 2010

AbstractUtilization of the industrial waste material benzyl (all‐R)‐cyclopenta[b]pyrrol‐2‐carboxylate 1a or its derivatives 1b, 1c as chiral auxiliaries is described. Allylation of nitrothioacetamides, proceeding by initial S‐allylation followed by a facile thio Claisen rearrangement, is accomplished with a diastereomeric ratio (dr) up to 85:15 using 1a, b as auxiliaries in stoichiometric amounts. Another aspect of this report is the diastereoselective synthesis of optically active amines, starting from aldehydes, with optical purities (op) up to 99%, Again a derivative of 1a was used as source of chirality.
Antibiotics from Gliding Bacteria, LXXV. Absolute Configuration and Biosynthesis of Tartrolon B, a Boron‐Containing Macrodiolide from Sorangium cellulosum
Authors: Schummer Dietmar , Schomburg Dietmar , Irschik Herbert , Reichenbach Hans , Höfle Gerhard 
Published: June 2010

AbstractThe absolute configuration of tartrolon B (1), a boron‐containing macrodiolide from Sorangium cellulosum, was established by X‐ray structure analysis as (2R,3R,4R,7S,8S,11S). Compared to the related boron‐containing macrodiolides boromycin (2), aplasmomycin (3), and borophycin (4), and identical substructure and configuration of the boron‐binding site was found for all four compounds. The biosynthesis of 1 was investigated by feeding experiments with 13C‐labeled precursors. According to NMR analyses, the carbon atoms from C‐1 to C‐18 are derived from acetate units, the two methyl groups at C‐22 and C‐23 are derived from methionine, and a three‐carbon starter unit C‐19 to C‐21 is derived from glycerol. The biosynthesis of 1 is closely related to those of 2 and 3 but with respect to the origin of the starter unit it is more distant to that of 4.