bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some aminophosphinocarboxylic acids and their derivatives
Authors: Mastryukova T. A. 
Published: January 2005

AbstractThe addition of Schiff bases of α‐aminoacid esters to vinylphosphoryl compounds was studied as a method for the synthesis of phosphinothricin and its analogues. The reaction was found to proceed smoothly in DMSO in the presence of strong nitrogen bases and under the conditions of phase transfer catalysis. The Claisen condensation of β‐phosphorylated propionitrile with diethyl oxalate was studied; phosphorylated derivatives of hydroxycitraconic acid nitrile were prepared on hydrolysis; transformation of such a derivative into a cyclic imide as well as into trimethylsilyl esters of these acids and their Z → E transformation were investigated. Cyclization reactions between α,ω‐dibromoalkanes and phosphoryl compounds containing an active methylene group affording cyclopropane and other cyclic derivatives were studied. The cyclopropane ring is cleaved by amines to give aminophosphinocarboxylic acids.
Application of phosphonate and thiophosphate analogues of nucleotides to studies of some enzyme reactions
Authors: Blackburn G. Michael , Ashton Peter R. , Guo Mao‐Jun , Rogers Michael , Taylor Graham , Guranowski Andrzej , Watts Donald 
Published: January 2005

AbstractThe enzymatic cleavage of a scissile PO bond can be blocked by recourse to phosphonate analogues of biological phosphate esters. α‐Fluorophosphonates have an enhanced electronegativity at the bridging carbon, which, in many cases, makes them superior to simple methylene phosphonates for the study of enzyme reactions. Thus, the β,γ‐difluoro‐methylene analogue of ATP is a good substrate for the interferon‐induced (2→5)An synthetase, which converts it into a (2→5)A4 species having a 5′‐β,γ‐difluoromethylenetriphosphate. This binds strongly to RNase L but does not activate it. The unsymmetrical Ap4Aases from Artemia and Lupin are strongly inhibited by P1,P4‐dithiophosphate analogues of diadenosyl‐5′,5‴‐P1,P4‐tetraphosphate although nonregiospecific cleavage of certain P2,P3‐methylene analogues can be observed. Some of these analogues are remarkably effective inhibitors of platelet aggregation and are effective inhibitors in vivo of arterial blood‐clotting in rabbits. Separation of all diastereoisomers of P1,P4‐dithiophosphate analogues of Ap4A is achieved cleanly using reverse‐phase hplc chromatography and this provides direct access to β,γ‐CHF‐bridged analogues of ATP with resolved stereochemistry at the CHF center. Lastly, growing cells of Dictyostelium discoideum not only tolerate a range of substituted methylene bisphosphonates in their growth medium but actually incorporate them into nucleotide analogues of ATP and Ap4A.
Enzymatic and chemical reactivities of sym‐monothiopyrophosphate
Authors: Halkides Christopher J. , Lightcap Eric S. , Frey Perry A. 
Published: January 2005

AbstractThe synthesis of sym‐monothiopyrophosphate (MTP) is described and the relative hydrolysis rate constants are reported for the dianion, trianion, and tetraanion in aqueous solution. The MTP‐dianion undergoes hydrolysis at a rate 5 x 107‐fold faster than the dianion of pyrophosphate (PPi) and the trianion undergoes hydrolysis 2.7 x 107‐fold faster than PPi‐trianion. The entropy of activation for the hydrolysis of MTP‐trianion is 0.2 cal/deg/mol, and the enthalpy of activation is 19.7 kcal/mol. The hydrolysis appears to involve a dissociative transition state. The hydrolysis of the tetramethyl ester of MTP, in contrast, appears to involve an associative transition state. The Mg complex of MTP is a reasonable substrate for PPi‐dependent phosphofructokinase and inorganic pyrophosphatase, despite its larger size relative to PPi. Therefore, MTP is tolerated within the active sites and in the transition states of enzymes that catalyze phosphoryl transfer from PPi to acceptor molecules. These observations are consistent with the transition states for these enzymes being dissociative in nature, although they do not prove that they are dissociative. MTP is, on the other hand, not a substrate for acetyl‐CoA synthase, an enzyme that utilizes the Mg complex of PPi as a specific acceptor for the adenylyl group, an alkylphosphoryl group. Inasmuch as nonenzymatic reactions of this type involve associative transition states, it may be that the larger size of MTP relative to PPi undermines the catalytic process in the active site of acetyl‐CoA synthase, which may catalyze adenylyl transfer through an associative transition state.
Conformational properties of cyclic pentaalkoxy phosphoranes: Apical–equatorial attachment and nonchair conformation of the phosphorus‐containing six‐membered ring
Authors: Yu Jaehoon , Sopchik Alan E. , Arif Atta M. , Bentrude Wesley G. , Roeschenthaler G.‐V. 
Published: January 2005

AbstractA series of phosphoranes with pentacovalent phosphorus contained in a 1,3,2‐dioxaphosphorinane ring have been studied by 1H NMR. One compound was investigated by low‐temperature 13C NMR and another by X‐ray crystallography. Although the 1H NMR parameters observed are time‐averaged, the coupling constants can be accounted for if the phosphoranes have the six‐membered ring attached apical–equatorial to phosphorus and occupy in solution rapidly isomerizing boat or slightly twisted boat conformations similar to that found in the X‐ray study.
Conformational transmission in pentacoordinated phosphorus systems, modelling the activated state of cyclic AMP
Authors: Broeders Niek L. H. L. , Koole Leo H. , Buck Henk M. 
Published: January 2005

AbstractThe proposed activated state of cyclic adenosine 3′,5′‐monophosphate (cAMP) is modelled by two nucleoside cyclic 3 ′,5 ′ Pv‐TBP compounds 3 and 4. The reason for the design of compound 3, in which a probe fragment (OCH2CH2OCH3 group) is linked to phosphorus, was reflected in a conformational transmission effect, which occurs when the probe is located in the axis of a Pv‐TBP. This means that the six‐membered 3′5′‐dioxaphosphorinane ring predominantly remains in a diequatorial (e,e) orientation. In the absence of conformational transmission, as in compound 4, the 3′,5′‐dioxaphosphorinane ring favors an equatorial‐axial (e,a) orientation. From this we conclude that the occurrence of conformational transmission can stabilize the (e,e) orientation of the 3′,5′‐ring. This can be of relevance to the activation of protein kinase by cAMP. In order to obtain more structural information from 3 and 4, we performed MNDO calculations on the models 8–10. These calculations revealed that the (e,e) orientation of the 3′,5′‐ring is destabilized by 3–4 kcal/mol compared to the (e,a) orientation. For the (e,a) geometry, the 3′,5′‐ring adopts a twist conformation, whereas the (e,e) orientated 3′,5′‐ring shows a half‐chair geometry.
Molecular modeling of the Wittig olefination reaction: Part 2: A molecular orbital approach at the MNDO‐PM3 level
Authors: Marí Frank , Lahti Paul M. , McEwen William E. 
Published: January 2005

AbstractWe have shown that the MNDO‐PM3 semiempirical molecular orbital method is capable of yielding calculated structures of oxaphosphetanes and ylides that are comparable with the experimentally known structures.The MNDO‐PM3 method also reproduces the geometric and thermodynamic parameters of the “mythyical Witting half‐reaction”, previously calculated using a more elaborate and costly ab initio molecular orbital approach. In addition, using the SADDLE routine, we were able to find a transition state for this half‐reaction. This transition state resembles geometrically the transition state found using the ab initio approach (4‐31G* level). The energy of activation was calculated to be 9.2 kcal/mole, which is fairly comparable with the ab initio reslt of 5.2 kcal/mole.According to our calculations, and in general agreement with findings of Volatron and Eisenstein [11], the mythical Witting reaction reaction would be expected to proceed through a planar transition state for the cycloaddition of the ylide and the aldehyde in a process that superficially seems to be a synchronous one. However, an analysis of the evolution of the bond orders and the localized molecular orbitals throughout the reaction indicates that the PO bond has not been formed in the transition state, whereas the CC bond is about 40% formed. Therefore, the mythical Wittig half‐reaction is best described as a very asynchronous cycloaddition (a bordeline two step mechanism) with a planar geometry in the transition state, composed of a multi‐centered mPCCO bond orbital and with the phosphorus and the oxygen atoms sharing a strong attractive charge interaction. A similar description results from computations of the Wittig reactions of H3CHCH3 and (C6H5)3PCHCH3 with H3CCHO, which is inconsistent with the Vedejs geometry.
Reaction of allyl bromide with carbonyl compounds mediated by tributylbismuthine [1]
Authors: Huang Yao‐Zeng , Liao Yi 
Published: January 2005

AbstractIn the presence of tributylbismuthine, allyl bromide was found to react with either aldehydes or ketones to give the corresponding homoallylic alcohols and their allylic ethers in good total yields.
Coupling constants in cis‐phosphine platinum complexes containing chalcogen‐nitride anions
Authors: Kelly Paul F. , Parkin Ivan P. , Sheppard Richard N. , Woollins J. Derek 
Published: January 2005

AbstractThe 31P NMR spectra of complexes of the type Pt(SeSN2)(PR3)2 and Pt(Se2N2(PR3)2) display trans 2J{77Se31P} couplings of ca. 30–80 Hz, with no corresponding cis coupling; in contrast Pt(TeSN2)(PMe2Ph2 has both trans and cis J{125Te31} coupling of 146 Hz and 103 Hz respectively. The 31 spectra of the complexes Pt(S215N2)(PMe2)P2 nd [Pt(S215N2)Cl(PMe2)Ph)]− show both 2J‐ and 4J{15N31P} couplings, which alter substantially upon protonation of the S2N22− ligand. The 15N NMR spectra of Pt(S215N2H)Cl(PMe2Ph) and Pt(S315N)Cl(PMe2Ph) show the presence of both 31P15N and 195Pt15N couplings but no significant 15N15N interactions.
X‐Ray and 31P CP MAS NMR studies of bis(dialkoxythiophosphoryl) disulfides
Authors: Potrzebowski Marek J. , Reinbenspies Joseph H. , Zhong Zhiang 
Published: January 2005

AbstractThe crystal and molecular structures of the title compounds were determined by X‐ray diffraction technique from diffractometer intensity measurements. It has been found that two homologous disulfides, bis(dimethoxythiophosphoryl) disulfide 1 and bis(dineopentoxythiophosphoryl) disulfide 2, form different molecular and crystal structures with space groups C2/c and P&1macr;, respectively. These results were confirmed by 31P CP MAS NMR studies, which showed that under favorable conditions the solid state NMR may lead to determination of the number of crystallographically unique phosphorus atoms. Moreover, the variation of the disulfide S–S bond length versus torsional P–S–S–P angles was observed.
Catalytic trimerization of isocyanates by neutral pentacoordinated silicon hydrides
Authors: Corriu Robert J. P. , Lanneau Gérard F. , Mehta Vimal D. 
Published: January 2005

AbstractPentacoordinated hydrosilanes react with excess of aryl isocyanates to give isocyanurates under mild and neutral conditions. The catalytic species are the initially formed N‐silylformamides, which incorporate three equivalents of isocyanate, and then rearrange to N‐silylformamide and isocyanurates.
Facile synthesis of 2,4‐dioxo‐1,2,3,4‐tetrahydroquinazolines by sulfur‐assisted carbonylation with carbon monoxide
Authors: Miyata Toshiyuki , Mizuno Takumi , Nagahama Yoshio , Nishiguchi Ikuzo , Hirashima Tsuneaki , Sonoda Noboru 
Published: January 2005

Abstract2,4‐Dioxo‐1,2,3,4‐tetrahydroquinazolines were easily synthesized in excellent yields by sulfur‐assisted carbonylation of 2′‐aminobenzamides with carbon monoxide in the presence of a base, such as DBU or DBN.
Does the ipso‐carbon chemical shift tell us anything about the structure of phenylated phosphorus compounds?
Authors: Liu Zi‐Ping , Schlosser Manfred 
Published: January 2005

AbstractThe nuclear magnetic resonance signals exhibited by the ipso‐carbon atoms of a variety of phenylated phosphorus compounds were found to span over the remarkably wide range of + 162 to + 117 ppm. Nevertheless, these changes in chemical shifts have little diagnostic value. They are tentatively attributed to a charge‐mediated contraction and expansion of the C,P σ‐bond orbital on one hand and to a σ‐bond induced deformation of the aromatic π‐electron cloud on the other.
Ligand exchange reactions of aryl pyridyl sulfoxides with grignard reagents: Convenient preparation of 3‐ and 4‐pyridyl grignard reagents and examination of the leaving abilities of pyridyl anions
Authors: Shibutani Tadao , Fujihara Hisashi , Furukawa Naomichi , Oae Shigeru 
Published: January 2005

AbstractAryl 3‐ and 4‐pyridyl sulfoxides undergo ligand exchange in reactions with aryl Grignard reagents to generate 3‐ and 4‐pyridyl Grignard reagents, which, upon treatment with aldehydes or ketones, give the corresponding addition products in moderate‐to‐good yields. The mechanism for the exchange reaction was investigated by treating optically active 3‐ and 4‐pyridyl p‐tolyl sulfoxides with a phenyl Grignard reagent. Inversion of the configuration of the sulfur atom was the stereochemical result of the reactions. In the reactions of phenyl 2‐pyridyl sulfoxide with Grignard reagents, the leaving ability of the 2‐pyridyl group competes with that of the phenyl group. Both the experimental and MO calculated enthalpy values for deprotonation of α‐, β‐, and γ‐protons of pyridine in the gas phase [1] are in accordance with the following order of the leaving abilities of aryl and pyridyl Grignard reagents: 4‐PyMgBr > 3‐PyMgBr » PhMgBr > p‐TolMgBr > 2‐PyMgBr.
Organoborane‐mediated synthesis of functional polymers: A review
Authors: Chung T. C. , Schulz D. N. 
Published: January 2005

AbstractThis article reviews recent advances in the synthesis of polar functional polymers via the mediation of organoborane monomers and polymers. Both direct polymerization and post‐polymerization functionalization processes are described. Organoborane‐assisted Ziegler–Natta, metathesis, and hydroboration (haloboration) polymerizations are presented. Moreover, the special problems and opportunities of polymer modification of olefin containing homo and copolymers by organoboranes are discussed.
Study of the reaction of methyltris(dimethylamino)silane with diamines
Authors: Cragg R. Harry , Ma C. Kit 
Published: January 2005

AbstractTris(dimethylamino)methylsilane reacts with N,N′‐dialkyldiamines to give the corresponding substituted 1,3,2‐diazasilacycloalkanes. In contrast, the reaction with an N‐alkyldiamine yields the corresponding polycyclic silazane.
The structure of tetramethyl μ‐monothiopyrophosphate
Authors: Halkides Christopher J. , Benning Matthew , Frey Perry A. 
Published: January 2005

AbstractThe compound tetramethyl μ‐monothiopyrophosphate (C4H12O6P2S) crystallizes in the monoclinic space group C 2/c, with (at ‐130°C) a = 10.322 Å, b = 8.229 Å, c = 12.062 Å, β = 98.44°, and Dcalc = 1.639 g/mL3 and Z = 4. The crystal structure has been determined by single crystal X‐ray diffraction to give a final R value of 0.0329 for 614 independent observed reflections [F˚ > 2.5σ(F˚)]. The sulfur atom resides on a crystallographic two‐fold axis. The PSP bond angle is 105.4° and the PS bond lengths are 2.093 Å. The bond angles around phosphorus range from 99.1° to 118.2°. The terminal PO bond is 1.465 Å, and the methoxyl PO bond is about 1.556 Å. The H3COP bond angle is about 119.5°. Many structural features are interpreted in terms of π‐bonding to phosphorus. Comparisons with the structures of pyrophosphate and related compounds indicate that the combined effects of increased acuteness of the PSP bond and the increased length of the P—S bonds lead to an increase of about 0.4 Å in the separation of phosphorus atoms in the sulfur‐bridging compound. These facts, together with the weakness of the PS bond, must be taken into account in the interpretation of kinetic data for enzymatic reactions of phosphorothiolates as substrates in place of phosphates.
Conformational study of 1,4‐thiazinan‐3‐one
Authors: Koskimies Jorma K. , Halonen Aija 
Published: January 2005

AbstractThe proton NMR spectra of several 1,4‐thiazinan‐3‐ones were analyzed using LAOCOON. The geminal and vicinal coupling constants indicate that the ring conformation of this heterocycle is a half‐chair similar to δ‐valerolactam. Molecular mechanics calculations show that the energy of the boat is only slightly higher than that of the half‐chair. The conformational equilibria of methyl‐substituted compounds were calculated by the coupling constant method. These energies are compared to those obtained by molecular mechanics.
Systematic series of azacycl[3.3.3]azines of varying nitrogen content: Nitrogen‐15 magnetic resonance spectra
Authors: Kanamori Keiko , Roberts John D. , Rossman Mitchell A. , Leonard Nelson J. 
Published: January 2005

AbstractNitrogen‐15 NMR spectra were obtained for a systematic series of azacycl[3.3.3]azines: 1,3,4,6,7,9‐hexaaza‐,1,3,4,6,7‐pentaaza‐,1,3,4,6‐tetraaza‐, 1,3,4,6,8‐pentaaza‐, and 1,3,6‐triazacycl[3.3.3]azine. The magnetic resonance data were compared with other physical and spectroscopic properties available for the series relative to the diminishing number of peripheral nitrogens in alternating positions. The properties of 1,3,4,6,8‐pentaazacycl[3.3.3]azine, which has a peripheral 1,4‐diazine‐type nitrogen, are distinct from those of the rest of the series.
Stereocontrolled enantioselective addition of diethylzinc to aldehydes using new chiral aminoalcohols
Authors: Kim Yong Hae , Park Doo Han , Byun Il Suk 
Published: January 2005

AbstractThe new chiral β‐aminoalcohols of indolinylmethanols (1) and their reduced derivatives (2) were synthesized from (S)‐indoline‐2‐carboxylic acid. Both (R) and (S) enantiomers of the optically active secondary alcohols have been successfully obtained in high enantiomeric excess from the stereoselective addition of diethylzinc to the aldehydes catalyzed by the chiral aminoalcohols (1 and 2). The sense of the asymmetric induction and the degrees of enantioselectivities turned out to be highly dependent on the structure of the catalysts: The presence of the catalyst 1 afforded the (S)‐configuration of the corresponding alcohols; on the other hand, the presence of 2 afforded the (R)‐configuration of the alcohols in high enantiomeric selectivity.
Preparation and reactions of 3‐oxa‐ and 4‐oxa‐5‐hexenyllithiums
Authors: Bailey William F. , Punzalan Eric R. , Zarcone Lyn M. J. 
Published: January 2005

AbstractLow‐temperature lithium–iodine exchange between tert‐butyllithium and the appropriate iodide has been used to generate 3‐oxa‐5‐hexenyllithium and a variety of 4‐oxa‐5‐hexenyllithiums. The 3‐oxa system is inherently unstable and fragments via facile β‐elimination to give the anion of allyl alcohol and ethylene. The 4‐oxa‐5‐hexenyllithiums, in contrast, are stable at low temperatures but undergo novel isomerization upon warming to deliver the lithium salt of a 4‐alken‐1‐ol in the formal equivalent of an unprecedented [1,4]‐Wittig rearrangement. The rearrangement is most likely mediated by 5‐exo‐trig ring closure of the 4‐oxa‐5‐hexenyllithium to a (2‐tetrahydrofuranyl)methyllithium followed by rapid opening to the alkoxide.
Heats of formation of organic molecules by ab initio methods: Thiaalkanes
Authors: Allinger Norman L. , Yang Linrong , Motoc Ioan , Bender Charles , Labanowski Jan K. 
Published: January 2005

AbstractThe bond energy scheme for calculating heats of formation of organic molecules from ab initio data (6–31G*) has been extended to include 24 compounds containing sulfur in the sulfide oxidation state. The rms deviation from the experimental values for these compounds is 0.54 kcal/mol, which is approximately experimental error.
Retention stereochemistry in ligand coupling reaction of optically active (1 R)‐phenylethyl 2‐quinolyl (R)‐ and (S)‐sulfoxide with methylmagnesium bromide
Authors: Uenishi Jun'ichi , Yamamoto Atsumi , Takeda Takashi , Wakabayashi Shoji , Oae Shigeru 
Published: January 2005

AbstractReactions of (+)‐(1R)‐phenylethyl 2‐quinolyl (R)‐ sulfoxide 7a and (−)‐(1R)‐phenylethyl 2‐quinolyl (S)‐ sulfoxide 7b with methylmagnesium bromide were examined. The reaction gave (R)‐2‐(1‐phenylethyl)quinoline 9 as a ligand‐coupling product, and a mixture of methyl(1R)‐phenylethyl(R)‐and (S)‐sulfoxide 11a and 11b as ligand exchange products. The other (S) stereoisomer at the 1‐phenylethyl carbon center was not detected in the reaction products. That is, both the ligand coupling and ligand exchange reactions proceeded with retention of configuration at the asymmetric carbon center.
Organophosphorus chemistry 23 [1], the reaction of α,β‐unsaturated nitriles with alkyl phosphites and phosphorus ylides
Authors: Mahran Mohamed R. , Abdou Wafaa M. , AbdEl‐Rahman Naglaa M. , Khidre Maha D. 
Published: January 2005

AbstractWittig reagents 2 react with furfurylidenemalonitrile (1a) and thienylidenemalonitrile (1b) to give a mixture of products (6 and 7). Compound 1b reacts with di‐alkyl phosphites (3) and trialkyl phosphites (4) to give the phosphonate 1:1 adducts 9 and 12, respectively. Structures of the new products were confirmed on the basis of elemental analyses and spectral studies.
Synthesis of fluorinated 2‐oxo‐1,4,2‐oxazaphosphol‐4‐ines and their opening by alcohols
Authors: Korenchenko Olga V. , Aksinenko Aleksey Yu. , Sokolov Vladimir B. , Martynov Ivan V. 
Published: January 2005

AbstractTrifluoromethyl‐substituted 1,4,2λ5‐oxazaphosphol‐4‐ines from phosphorus dichlorides and N‐acylimines of hexafluoroacetone have been synthesized and characterized by 1H, 19F, and 31P NMR. Alcohols open these oxazaphospholines at the P–O bond, forming the corresponding esters.
5‐Methyl‐2‐phenyl‐2H‐1,2,3‐diazaarsole in reaction with ethyl diazoacetate
Authors: Arbuzov Boris A. , Zabotina Elena Ya. , Dianova Evelina N. , Litvinov Igor A. , Naumov Victor A. , Latypov Shamil K. , Il'asov Ahat V. 
Published: January 2005

Abstract5‐Methyl‐2‐phenyl‐2H‐ 1,2,3‐diazaarsole 1 reacts with ethyl diazoacetate to form a 1:1 bicyclic product 3a, 8‐ethoxycarbonyl‐4‐methyl‐2‐phenyl‐1‐arsa‐2,3,6,7‐tetraazabicyclo[3.3.0]octa‐3.7‐diene. The latter isomerizes to a two‐coordinate arsenic compound 5, 3‐ethoxycarbonyl‐5‐[α‐(phenylhydrazono)ethyl] 1‐1,2,4‐diazaarsole. The X‐ray crystal structure analyses of both products 3a and 5 have been carried out.
(2,4,6‐Tri‐tert‐butylphenylimino)thioxo‐and ‐selenoxophosphoranes. Synthesis and structural characterization
Authors: Romanenko Vadim D. , Ruban Alexander V. , Drapailo Andrei B. , Chernega Alexander N. , Rusanov Eduard B. 
Published: January 2005

AbstractA series of stable imino(chalcogeno)phosphoranes R  P( X)  NAr, RPh, 2, 4, 6‐Me3C6H2, 2, 4, 6‐i‐Pr3C6H2; Ar 2, 4, 6‐t‐Bu3C6H2; X  S, Se (5bd, 6b,c), has been prepared by the oxidation of λ3‐imino‐phosphines R  P  N  Ar (4b‐d) with sulfur and selenium. When P  (tert‐butyl)iminophosphine, t‐Bu  P  N‐  Ar (4a), was reacted with S8 and Seiv the corresponding oligomeric metaphosphonimidates 7, 8 were obtained. All new compounds are characterized by their NMR spectra. The constitution of the imino(thioxo)phosphorane 5d is proved by X‐ray crystal structure determination.
Syntheses of stereodefined β‐alkylidene‐γ‐lactones and substituted β, γ‐unsaturated δ‐lactones
Authors: Lee Yuhshan , Leong William , Zweifel George 
Published: January 2005

Abstract1‐Trimethylsilyl‐1,3‐diyne derived trans‐bis(trimethylstannyl) enynes undergo stepwise transmetallation with methyllithium to furnish the corresponding enynyllithium reagents. The application, in various orders, of a sequence of transmetallation‐protonation‐alkylation‐hydroxyalkylation‐hydroboration‐oxidation reactions provides a novel approach to stereo‐defined β‐alkylidene γ‐lactones and β, γ‐unsaturated δ‐lactones.