NaBH4 In MeOH Research Articles

Expeditious access to cis-β-aryl, γ-alkyl disubstituted (±)-γ-butyrolactones via nickel-hydride catalysis.

The 1,4-reduction of β- and γ-substituted butenolides using 5 mol% of NiCl2·6H2O and NaBH4 in MeOH for rapid access to cis-β,γ-disubstituted γ-butyrolactones is described. The reaction was selective for cis-products, which were obtained in good to excellent yields. This study showcased the influence of steric hindrance and angle strain on the diastereoselectivity outcome of conjugate reductions facilitated by in situ generated nickel-hydride.

Novel Chiral PNNP Ligands with a Pyrrolidine Backbone – Application in the Fe‐Catalyzed Asymmetric Transfer Hydrogenation of Ketones

The PNNP ligand (R,R)‐{PPh2(2‐C6H4)CH=N(pyrrolidine‐NBn)‐}2 2 was prepared by condensation between 2‐diphenylphosphino benzaldehyde and the pyrrolidine‐substituted diamine 1. Reduction with NaBH4 in MeOH afforded (R,R)‐{PPh2(2‐C6H4)CH–NH(pyrrolidine‐NBn)‐}2 3. The corresponding iron(II) complexes [FeCl2(2)] (4), [Fe(CH3CN)2(2)](BF4)2 (5) and [Fe(CH3CN)2(2)](PF6)2 (6) were synthesized and fully characterized by NMR, ESI‐HRMS, and EA. DFT calculations for complexes [FeCl2(2)] (4) and [Fe(CH3CN)2(2)](BF4)2 (5) were carried out in order to investigate the stability of related structures. The PNNP ligands 2 and 3 in combination with Fe3(CO)12 as iron source were tested as catalysts in the asymmetric transfer hydrogenation of a variety of ketones with conversions higher than 95 % and enantioselectivities up to 97 %.

ChemInform Abstract: Stereoselective Synthesis of 5a-Ethyl-1,2,3,3a,4,5,5a,6,9a,9b-decahydro-1,3,4-trihydroxy-3a- (hydroxymethyl)-7H-benz[e]inden-7-one Derivatives.

Homochiral Diels-Alder cyclodimerization of (+/-)-6-ethenyl-7-oxabicyclo[2.2.1]hept-5-en-2-endo-ol followed by oxidation gives (1RS,4RS,4aSR,4bSR,5RS,8RS,8aRS)-8a-ethenyl-1,3,4a,4b,5,6,8,8a,9-decahyd ro-11,4:5,8-diepoxyphenanthrene-2,7-dione (18). Selective hydrogenation followed by epoxidation produced (1RS,4RS,4aRS,5aRS,6aRS,7RS,10RS,10aSR,10bRS)-6a-ethyl-1,4,5a,6,6a,7,9,1 0,10a,10b-decahydro-1,4:7,10-di-epoxyphenanthro[8a,9b]oxirene-3,8-dione (21), which was solvolyzed (Me3SiOSO2CF3, Piv2O) with concomitant pinacol rearrangement involving an acyl-group migration to give a 6-oxo-7-oxabicyclo[2.2.1]hept-2-yl cation intermediate, which finally generated (1RS,3SR,3aRS,4SR,5aRS,6RS,9RS,9aSR,9bSR)-5a-ethyl-1,4,5,5a,6, 7,8,9,9a,9b-decahydro-7,10-dioxo-3H-6,9-epoxy-1,3a-ethanonaphtho[1,2-c]f uran-3.4-diyl bis(2,2-dimethylpropa noate) (24). Photo-reductive 7-oxa bridge opening of 24, followed by water elimination and silylation, provided (1RS,3SR,3aRS,4SR,5aSR,9aSR,9bSR)-7-{[(tert-butyl)dimethylsilyl]oxy}-5a- ethyl-1.4,5,5a,9a,9b-hexahydro-10-oxo-3H- 1,3-ethanonaphtho[1,2-c]furan-3,4-diyl bis(2,2-dimethylpropanoate) (34). Reduction of 34 with NaBH4 in MeOH followed by desilylation and alcohol protection produced (1RS,3RS,3aRS,4SR,5aSR,9aSR, 9bSR)-5a-ethyl-2,3,3a,4,5,5a,6,7,9a,9b-decahydro-1,3-bis(methoxymethoxy) -3a-[(methoxymethoxy)methyl]-7-oxo-1H-benz[e] inden-4-yl 2,2-dimethylpropanoate (5), a polyoxy-substituted decahydro-1H-benz[e]indene derivative with cis-transoid-trans junction for the two cyclohexane and the cyclopentane rings bearing an angular 3a-(oxymethyl) substituent.

Alkylation of Pyrrolidine‐2,5‐dione with 2‐(3,4‐Dihydro‐1‐napthalenyl)ethyl‐4‐methylphenylsulphonates: A New and General Approach to 13‐Azaequilenin Analogs

Pyrrolidine‐2,5‐dione was N‐alkylated with three different 2‐(3,4‐dihydro‐1‐napthalenyl)ethyl‐4‐methylphenylsulphonates to give the corresponding seco‐azasteroids which on chemoselective dehydrogenation, reduction with NaBH4 in MeOH at 0°C gave the corresponding 5‐hydroxy‐2‐pyrrolidones. Intramolecular cyclization of these 5‐hydroxy‐2‐pyrrolidones afforded the corresponding title compounds.

Stereoselective Synthesis of 5a-Ethyl-1,2,3,3a,4,5,5a,6,9a,9b-decahydro- 1,3,4-trihydroxy-3a-(hydroxymethyl)-7H-benz[e]inden-7-one Derivatives

Homochiral Diels-Alder cyclodimerization of (+/-)-6-ethenyl-7-oxabicyclo[2.2.1]hept-5-en-2-endo-ol followed by oxidation gives (1RS,4RS,4aSR,4bSR,5RS,8RS,8aRS)-8a-ethenyl-1,3,4a,4b,5,6,8,8a,9-decahyd ro-11,4:5,8-diepoxyphenanthrene-2,7-dione (18). Selective hydrogenation followed by epoxidation produced (1RS,4RS,4aRS,5aRS,6aRS,7RS,10RS,10aSR,10bRS)-6a-ethyl-1,4,5a,6,6a,7,9,1 0,10a,10b-decahydro-1,4:7,10-di-epoxyphenanthro[8a,9b]oxirene-3,8-dione (21), which was solvolyzed (Me3SiOSO2CF3, Piv2O) with concomitant pinacol rearrangement involving an acyl-group migration to give a 6-oxo-7-oxabicyclo[2.2.1]hept-2-yl cation intermediate, which finally generated (1RS,3SR,3aRS,4SR,5aRS,6RS,9RS,9aSR,9bSR)-5a-ethyl-1,4,5,5a,6, 7,8,9,9a,9b-decahydro-7,10-dioxo-3H-6,9-epoxy-1,3a-ethanonaphtho[1,2-c]f uran-3.4-diyl bis(2,2-dimethylpropa noate) (24). Photo-reductive 7-oxa bridge opening of 24, followed by water elimination and silylation, provided (1RS,3SR,3aRS,4SR,5aSR,9aSR,9bSR)-7-{[(tert-butyl)dimethylsilyl]oxy}-5a- ethyl-1.4,5,5a,9a,9b-hexahydro-10-oxo-3H- 1,3-ethanonaphtho[1,2-c]furan-3,4-diyl bis(2,2-dimethylpropanoate) (34). Reduction of 34 with NaBH4 in MeOH followed by desilylation and alcohol protection produced (1RS,3RS,3aRS,4SR,5aSR,9aSR, 9bSR)-5a-ethyl-2,3,3a,4,5,5a,6,7,9a,9b-decahydro-1,3-bis(methoxymethoxy) -3a-[(methoxymethoxy)methyl]-7-oxo-1H-benz[e] inden-4-yl 2,2-dimethylpropanoate (5), a polyoxy-substituted decahydro-1H-benz[e]indene derivative with cis-transoid-trans junction for the two cyclohexane and the cyclopentane rings bearing an angular 3a-(oxymethyl) substituent.

Synthesis and Reaction of New Metal Cluster Complexes Containing a Wrucose Core

Several chiral cluster derivatives, RuCoW(μ3Se)(CO)8{η5-C5H4C(O)R} [R = H (2), CH3 (3), C6H5 (4), C6H5C(O)OCH3 (5)], were” synthesized by reaction of the precursor (μ3-Se)RuCo2(CO)t) (1) with the functionally substituted cyclopentadienyl tricarbonyl metal complex anions [W(CO)3{η5-C5H4C(O)R}]−without using benzophenone ketyl. A new double-tetrahedral cluster compound, p-[(μ3-Se)(CO)8RuCoW(μ5-C5H4C(O))]2C6H4 (6), was obtained by treating (1) with a metal exchange reagent, Na2[W(CO)3(η5-C5H4)C(O)C6H4C(O)(η5-C5H4)}(CO)3WJ. Cluster (3) reacted with NaBH4 in MeOH to give the secondary alcohol cluster RuCoW(μ3-Se)(CO)8{η5-C5H4CH(OH)CH3} (7). The cluster (3) reacted with Na2Fe(CO)4 in refluxing THF followed by the treatment of 40% H3PO4 to yield the new cluster HRuFeW(μrSe)(CO)8{η5-C5H4C(O)CH3} (8). The structure of cluster (3) has been determined by single-crystal X-ray diffraction. Crystal data for cluster (3) give an orthorhombic space group Pbca, a - 26.326(4) Å, b = 18.231(4) Å, c = 15.956(3) Å, V = 7658(4) Å3, Z = 16, R = 0.029 and R w = 0.036.

Unusual sugars of the GPL-type antigen of Mycobacterium avium serovar 19. Stereoselective synthesis of methyl 6-deoxy-3-C-methyl-2,4-di-O-methyl-α-L-mannopyranoside and its C-4 epimer

Completely reversed stereoselectivity of reduction of methyl 6-deoxy-2,3-O-isopropylidene-3-C-methyl-α-L-mannopyranoside (2) and its deisopropylidenated derivative (7) was observed. Compound 2 gave exclusively the L-talo-isomer (3) with NaBH4 in MeOH, but the reduction of 7 with NaBH4 in acetic acid resulted in the L-manno-derivative 8. It is assumed that in the first case the stereoselectivity is determined by the steric accessibility of the carbonyl group, while in the second case free OH-groups direct the selectivity of the reduction by complexation or ligand exchange.

Neutral and cationic ruthenium hydrotris(pyrazolyl)borate derivatives containing bulky monodentate phosphines. Crystal structures of [RuTp(H2O)(PPri2Me)2][CF3SO3]·EtOH and [RuTp(N2)(PEt3)2][BPh4

The complexes [RuTp(Cl)(PPri2Me)2] 1 and [RuTp(Cl)(PEt3)2] 2 were prepared by thermal displacement of PPh3 from [RuTp(Cl)(PPh3)2] by the corresponding phosphine. A series of cationic complexes of the type [RuTp(L)(PR3)2]+ (L = H2O, N2 or CNBut; PR3 = PPri2Me or PEt3) was obtained by chloride abstraction from 1 or 2 in the presence of L. As consequence of the steric crowding, one of the PPri2Me ligands in 1 is labile, and it was readily replaced by neutral molecules such as MeCN or CNBut to yield the neutral complexes [RuTp(Cl)L(PPri2Me)] (L = MeCN or CNBut). The monohydrides [RuTp(H)(PPri2Me)2] and [RuTp(H)(PEt3)2] were obtained by treatment of 1 or 2 with NaBH4 in MeOH. Protonation of these monohydrides led to the cationic dihydrogen complexes [RuTp(H2)(PPri2Me)2]+ and [RuTp(H2)(PEt3)2]+ which were isolated as [BPh4]– salts, and characterized by determination of their (T1)min and 1JHD coupling constants in the corresponding isotopomers. The neutral hydride(dihydrogen) complex [RuTp(H)(H2)(PPri2Me)], which resulted from the reaction of [RuTp(Cl)(MeCN)(PPri2Me)] with NaBH4 in MeOH, was characterized in analogous fashion. The crystal structures of the complexes [RuTp(H2O)(PPri2Me)2][CF3SO3]·EtOH and [RuTp(N2)(PEt3)2][BPh4] were determined.

Synthesis and characterisation of manganese(II) compounds with tetradentate ligands based on the bispidine backbone

Reaction of the tetradentate ligand dimethyl 3,7-dimethyl-9-oxo-2,4-bis(2-pyridyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate (L1) with manganese(II) chloride or iodide in methanol yielded [MnL1Cl2] and [MnL1I2], respectively. Reaction with silver(I) triflate Ag(O3SCF3) converted these compounds into [MnL1(O3SCF3)2]. Reduction of L1 with NaBH4 in MeOH and LiAlH4 in THF led to the triol 1,5-bis(hydroxymethylene)-3,7-dimethyl-2,4-bis(2-pyridyl)-3,7-diazabicyclo[3.3.1]nonan-9-ol (L2); the reduction is stereoselective and yields the syn isomer. Complexation of manganese(II) chloride and iodide with L2 produced [MnL2Cl2] and [MnL2I2] and these have a higher thermal stability than [MnL1X2]. The complexes [MnL1Cl2], [MnL1I2], [MnL1(O3SCF3)2], [MnL2Cl2] and [MnL2I2] are characterised spectroscopically, electrochemically and by their magnetic, conductometric, thermal and structural properties (X-ray analyses of [MnL1Cl2] and [MnL2Cl2]).

Ring-methyl activation in pentamethylcyclopentadienyl complexes 7 reactions of [Ru(η2:η5-C5Me4CH2O(CH2)nCH=CHR2)(CO)2]+BF4ȡ with nucleophiles

The ruthenium chelates containing tethered olefinic side chains [Ru(η2:η5-C5Me4CH2O(CH2)nCH=CHR2)(CO)2]+BF4ȡ (1a, R2 = H, n = 1; 1b, R2 = Me, n = 1; 1c, R2 = H, n = 2) react with NaBH4 in MeOH or in water to give the non-chelated olefin hydride complexes [Ru(η5-C5Me4CH2O(CH2)nCH=CHR2)(CO)2(H)] (2aȁc). By contrast, alkoxide attacked at a carbonyl ligand in 1a giving the chelated olefin alkoxycarbonyl complexes [Ru(η2:η5-C5Me4CH2OCH2CH=CH2)(η1-COOR3)(CO)](3a,aȃ, R3 = Me; 4a,aȃ, R3 = Et), which form a separable mixture of diastereomers. There was no evidence for attack at the coordinated olefin in complex 1.

Long‐distance control in stereoselective reduction of 3‐[3‐(4′‐bromo[1,1′‐biphenyl]‐4‐yl)‐3‐keto‐1‐phenylpropyl]‐4‐hydroxy‐2H‐1‐benzopyran‐2‐one: Relative configuration of prevailing diastereomer and absolute configuration of its enantiomers

Depending on the reducing agent and reaction conditions, diastereoselective reduction of 3-[3-(4′-bromo[1,1′-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one (2) proceeds with different stereoselectivity; a surprisingly high, approximately 90% d.e. of 4A is achieved with NaBH4 in MeOH at low temperature. Resulting diastereomeric racemates 4A and 4B are separated and their respective syn and anti configurations are assigned on the bases of mechanic considerations, supported by the 1H-NMR spectra and conformational analysis based on MM2 calculations. The syn diastereomer 7A, 4-OMe derivative of 4A, was partially resolved by acylation at C(3)-OH with S-(−)-camphanic acid to camphanyl ester 12 of (−)-7A, leaving (+)-enantiomer 7A. The assignment of absolute 1R,3S-configuration to (−)-7A is based on comparison of its CD spectrum with those of the model compounds S-14 and R-15, which represent partial chromophores 4-hydroxy-2H-1-benzopyran-2-one (4-hydroxycoumarin) A, and 4′-bromo-1,1′-biphenyl B; their exciton coupling in (−)-7A is suggested. Chirality 9:512–522, 1997. © 1997 Wiley-Liss, Inc.

Long-distance control in stereoselective reduction of 3-[3-(4?-bromo[1,1?-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one: Relative configuration of prevailing diastereomer and absolute configuration of its enantiomers

Depending on the reducing agent and reaction conditions, diastereoselective reduction of 3-[3-(4′-bromo[1,1′-biphenyl]-4-yl)-3-keto-1-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one (2) proceeds with different stereoselectivity; a surprisingly high, approximately 90% d.e. of 4A is achieved with NaBH4 in MeOH at low temperature. Resulting diastereomeric racemates 4A and 4B are separated and their respective syn and anti configurations are assigned on the bases of mechanic considerations, supported by the 1H-NMR spectra and conformational analysis based on MM2 calculations. The syn diastereomer 7A, 4-OMe derivative of 4A, was partially resolved by acylation at C(3)-OH with S-(−)-camphanic acid to camphanyl ester 12 of (−)-7A, leaving (+)-enantiomer 7A. The assignment of absolute 1R,3S-configuration to (−)-7A is based on comparison of its CD spectrum with those of the model compounds S-14 and R-15, which represent partial chromophores 4-hydroxy-2H-1-benzopyran-2-one (4-hydroxycoumarin) A, and 4′-bromo-1,1′-biphenyl B; their exciton coupling in (−)-7A is suggested. Chirality 9:512–522, 1997. © 1997 Wiley-Liss, Inc.

Reductive alkylation of 9-amino-xanthen-3-yloxymethylpoly(styrene): a novel procedure for the synthesis of peptidyl N-alkyl amides by Fmoc/But chemistry

Reductive N-alkylation of the ‘amide’ anchor resin, 9-amino-xanthen-3-yloxymethyl poly(styrene)1, by sequential treatment with alkyl aldehydes under mild acidic conditions followed by NaBH4 in MeOH–DMF, and then followed by optimised Fmoc/But solid-phase peptide synthetic procedures afforded an unique class of peptidyl N-alkyl amides in excellent yields.

ChemInform Abstract: Diastereoselectivity in the Reduction of Sterically Unbiased 2,2‐Diarylcyclopentanones.

AbstractReduction of the sterically unbiased title compounds with either NaBH4 in MeOH or LiBH4 in THF produces diastereomeric cyclopentanols (II) and (III) in varying cis/trans ratios.

Inevitable generation of primary alcohols during reduction of oxidized lipids with sodium borohydride.

This report deals with the fluorometric determination of fatty alcohols generated by the reduction of the ester linkage of lipids with NaBH4, and with the limitations of the reduction method for assaying oxidized lipids. Optimum conditions for the fluorometric analysis of primary and secondary alcohols using 1-anthroyl nitrile were obtained. After reduction with NaBH4 in MeOH or in MeOH/benzene (8∶2, v/v), the formation of 1-hexadecanol from a variety of palmitic acid esters was measured fluorometrically by reverse-phase high-performance liquid chromatography (HPLC): From glycerides and methyl palmitate, 1-3% (w/w) 1-hexadecanol was produced and a trace was produced from cholesteryl palmitate (10 min, 21°C). 1-Hexadecanol was never generated from palmitic acid. Although considerable improvement occurred with the choice of the solvent for the NaBH4 reduction, the generation of primary alcohols from ester lipids usually seems inevitable.

Purines. XLI. An alternative synthesis and the chemical behavior of 7,9-dialkyladeninium salts.

A full account is given of the chemical behavior observed for 7, 9-dialkyladeninium salts (16). On treatment with boiling 1N aqueous NaOH for 60min, 16a, b, d, e (X=I), 16c (X=Br), and 16f (X=ClO4) rearranged to isomeric N6, 7-dialkyladenines (21a-f) in 50-91% yields. Treatment of the salts with 0.5N aqueous Na2CO3 at room temperature for 30-90min or with Amberlite CG-400 (OH-) in H2O at room temperature gave the ring-opened derivatives 22a-f (in the trans-formamide form) in 56-83% yields, and rate constants for the ring-opening reactions of 16a, b, d-g (X=ClO4) and 16c (X=Br) leading to 22a-g were determined in H2O at pH 9.84 and ionic strength 0.50 at 25°C. Cyclization of 22a with NaH in AcNMe2 at room temperature or with boiling 1N aqueous NaOH produced 21a in 84% or 72% yield, respectively.In solution, the trans-formamides 22 seemed to transform slowly into the cis-formamides 23, attaining equilibria. The existence of such an equilibrium in D2O or Me2SO-d6 at 25°C or in H2O at pH 9.84 and ionic strength 0.50 at 25°C was kinetically confirmed in the case of 22a, and the mechanism of the rearrangement of 16 to 21 through 22 is discussed on the basis of the above kinetic results and Deslongchamps' theory of stereoelectronic control. On treatment with NaBH4 in MeOH at room temperature, 16a (X=I) furnished the 7, 8-dihydro derivative 28 (84% yield), which slowly decomposed in H2O at 60°C to give 22a in 49% yield.The 7, 9-dialkyladeninium salts (16) were found to be obtainable from N'-alkoxy-1-alkyl-5-formamidoimidazole-4-carboxamidines (9) through an alternative synthetic route : Alkylations of 9 with alkyl halides in HCONMe2 in the absence of base, followed by hydrogenolysis of the N'-alkoxy group and cyclizatio (or vice versa) produced 16 in acceptable yields. In order to interpret the proton nuclear magnetic resonance spectrum of 22a, the 2-deuterated species 26 was also synthesized from 24 via 25 and 27.

ChemInform Abstract: (Dialkylamino)phosphorus Metal Carbonyls. Part 5. Chemical Reactivity of the Phosphorus‐Bridging Carbonyl Group in Carbonylbis((diisopropylamino)phosphido)hexacarbonyldiiron.

AbstractTreatment of the title compound (I) with NaBH4 in MeOH results in reduction of the P‐bridging CO group to give the corresponding sec. alcohol (IIa).

ChemInform Abstract: A General Synthetic Route for Platinum Cluster Compounds Containing Carbonyl and Tertiary Phosphine Ligands and a Study of Their Reactions with Unsaturated Inorganic Molecules.

AbstractThe reduction of complexes such as (I) by zinc dust or NaBH4 in MeOH or acetone under a CO atmosphere is an efficient method for the formation of polynuclear complexes (II)‐(IV) which is superior in yield convenience and generality to other methods and applicable for compounds (I) containing tert. phosphine ligands with a variety of alkyl or aryl groups.

Übergangsmetall-Komplexe mit Schwefelliganden, XXVII Synthese und Reaktivität der Nitrosyl-und Nitrido-Ruthenium-Komplexe mit 1,2-Benzoldithiolat-Liganden [Ru(NO)(S2C6H4) 2]- bzw. [Ru(N)(S2C6H4)2]- / Transition Metal Complexes with Sulfur Ligands, XXVII Synthesis and Reactivity of the Nitrosyl- and Nitrido-Ruthenium Complexes with 1,2-Benzenedithiolate Ligands [Ru(NO)(S2C6H4)2]- and [Ru(N)(S2C6H4)2]-, Respectively

The reaction of [Ru(NO)2(PPh3)2], [RuCl(NO)2(PPh3)2]PF6 or [RuCl3(NO)(PPh3)2] with 1,2- benzenedithiolate(-2), C6H4S2 2-, leads to the 16e--complex [Ru(NO)(S2C6H4)2]-, which was isolated as the NBu4 + salt (1). The square pyramidal anion in [NBu4)[Ru(NO)(S2C6H4)2] coordinates PMe3 with rearrangement of the sulfur ligands to give the six-coordinate cis- [NBu4][Ru(NO)(PMe3)(S2ChH4)2] (3); the rearrangement of the C6H4S2 2--Iigands from trans to cis coordination is proved by 13C NMR spectroscopy. [Ru(NO)(S2C6H4)2]- is rapidly reduced even under mild conditions. Reaction of 1 with NaBH4 in MeOH leads to the reduction of NO to a nitrido ligand and the concomitant oxidation of (formal) Ru(III) to Ru(VI) yielding [NBu4][Ru(N)(S2C6H4)2] (2). This compound is also formed when the nitrosyl complex is reacted withSiMe3N3.[Ru(NO)2(PPh3)2] and [RuCl(NO)2(PPh3)2]PFare denitrosylated by dttd2- (dttd2- = 2,3,8,9-dibenzo-1,4,7,10-tetrathiadecane(-2)) to give [Ru(dttd)(PPh3)2]

ChemInform Abstract: Models for the Triply Bridging Site in Chemisorption: The First Complex Containing the Pt3(μ3‐H) Group and Evidence for Inversion of the Pt3(μ3‐H) Unit and for Reversible Coordination of CO.

AbstractReaction of (I) as the trifluoroacetate salt with NaBH4 in MeOH gave first (II) and then (III) as monitored by 31P NMR spectroscopy.