Synthesis of phosphonate and phostone analogues of ribose-1-phosphates

Article abstract of DOI:10.3762/bjoc.5.37

The synthesis of phosphonate analogues of ribose-1-phosphate and 5-fluoro-5-deoxyribose-1-phosphate is described. Preparations of both the a- and β-phosphonate anomers are reported for the ribose and 5-fluoro-5- deoxyribose series and a synthesis of the c

Full text of DOI:10.3762/bjoc.5.37

Synthesis of phosphonate and phostone analogues
of ribose-1-phosphates
Pitak Nasomjai, David O’Hagan* and Alexandra M. Z. Slawin
Full Research Paper
Open Access
Address:
Beilstein Journal of Organic Chemistry 2009, 5, No. 37.
School of Chemistry and Centre for Biomolecular Sciences, University
of St Andrews, North Haugh, St Andrews, Fife, KY16 9ST, UK
doi:10.3762/bjoc.5.37
Received: 25 May 2009
Accepted: 08 July 2009
Published: 27 July 2009
Email:
David O’Hagan* - do1@st-andrews.ac.uk
* Corresponding author
Associate Editor: S. Flitsch
Keywords:
© 2009 Nasomjai et al; licensee Beilstein-Institut.
License and terms: see end of document.
5-fluoro-5-deoxyribose-1-phosphate; fluorometabolite biosynthesis;
phosphonates; phostone; ribose-1-phosphate
Abstract
The synthesis of phosphonate analogues of ribose-1-phosphate and 5-fluoro-5-deoxyribose-1-phosphate is described. Preparations
of both the α- and β-phosphonate anomers are reported for the ribose and 5-fluoro-5-deoxyribose series and a synthesis of the
corresponding cyclic phostones of each α-ribose is also reported. These compounds have been prepared as tools to probe the details
of fluorometabolism in S. cattleya.
Introduction
Fluoroacetate (1) and 4-fluorothreonine (2) are unusual for a ring opening isomerisation reaction converting 5-fluoro-5-
secondary metabolites in that they contain a fluorine atom. They deoxyribose-1-phosphate (5) to 5-fluoro-5-deoxyribulose-1-
are elaborated by the bacterium Streptomyces cattleya as part of phosphate (6). Further processing to fluoroacetaldehyde (7) and
its defense strategy since 4-fluorothreonine (2) has antibiotic then conversion to fluoroacetate (1) and 4-fluorothreonine (2)
activity and fluoroacetate (1) is a toxin [1]. The biosynthetic complete the pathway. The focus of this research involved
pathway from fluoride ion to these fluorometabolites has largely generating a potential inhibitor of either the PNP or the
been elucidated and is summarised in Scheme 1 [2].
subsequent isomerase enzymes as a tool, to try to accumulate
biosynthesis intermediates in cell free extract studies [3]. We
The first committed step in the biosynthesis involves the fluor- have already demonstrated that the S. cattleya PNP can depur-
inase, an enzyme that catalyses nucleophilic attack of fluoride inate both 5′-FDA and adenosine, and thus the presence or
ion on SAM (3) to generate 5′-FDA (4). The initial fluorinated absence of fluorine at the C-5′-position is not a requisite for
product 5′-FDA (4) is then depurinated by a purine nucleotide catalysis. The next enzymatic step involves a ring opening
phosphorylase (PNP) to give 5-fluoro-5-deoxyribose-1-phos- isomerisation of the ribose-1-phosphate 5. In this paper we
phate (5). This phosphate intermediate becomes the substrate report the synthesis of phosphonate analogues 8 and 9 of ribose-
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Beilstein Journal of Organic Chemistry 2009, 5, No. 37.
Scheme 1: Biosynthetic pathway from fluoride ion to fluoroacetate 1 and 4-fluorothreonine 2 in S. cattleya [2].
1-phosphate 5 where the linking phosphate oxygen has been (13). For each route the key synthetic steps are the same
replaced by a methylene group and for 9 the fluorine has been involving installation of the dimethyl phosphonate moiety on a
replaced by OH (see Figure 1). These phosphonates were 2,3-O-isopropylidene ribofuranoside via a Wadsworth-Emmons
considered as candidate inhibitors for either the PNP or the reaction [4]. Route A (Scheme 2) started with acetonide protec-
isomerase enzyme, with potential utility as tools to interrogate tion of D-ribonic-γ-lactone (12) to generate 2,3-isopropylidene
the biosynthesis system, and as inert candidate substrate 14 [5]. Fluorination of the free 5-hydroxyl group with Deoxo-
analogues for enzyme co-crystallisation studies. We also report fluor™ [6] gave 5-deoxy-5-fluoro-2,3-O-isopropylidene-D-
the synthesis of the cyclic phostone analogues 10 and 11 ribonic-γ-lactone (15) in good yield and then subsequent reduc-
(Figure 1), which were viewed also as potential substrate tion of lactone 15 with NaBH4 resulted in the fully reduced diol
analogues for co-crystallisation studies, particularly with the 16. Diol 16 has been previously synthesised [7], however this
isomerase enzyme which converts 5 to 6 during the biosyn- route appears to offer a more efficient preparation. In our case,
thesis.
even with limiting NaBH4, mixtures of diol 16 and 5-deoxy-5-
fluoro-2,3-ribofuranoside 17 were obtained, however treatment
with DIBAL-H at 40 °C [8] gave a clean reaction and
5-fluororibofuranoside 17 was recovered in moderate yield.
Finally a Wadsworth-Emmons reaction [4] of 17 using tetra-
methyl methylenediphosphonate in DCM/aq. NaOH gave a
smooth conversion to 5-fluorophosphonate 18 which had an α:β
ratio of 3.2:1. (The major α-anomer was assigned for 18 based
on the subsequent NMR assignments of 23a and b, see below.)
These diastereoisomers were inseparable by conventional chro-
matography.
Figure 1: Synthesized phosphonates 8 and 9 and cyclic phostones 10
and 11.
Results and Discussion
Due to the inability to separate α−18 from β−18, route B
The target phosphonates 8 and 9 have been prepared by routes (Scheme 3) was explored as an alternative. Following the
A and B as shown in Scheme 1 and Scheme 2 respectively. The protocol demonstrated by Meyer et al. [4], 5-O-trityl-phosphon-
routes start either from D-ribonic-γ-lactone (12) or D-ribose ates 21a and 21b were obtained as individual epimers after
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Beilstein Journal of Organic Chemistry 2009, 5, No. 37.
Scheme 2: Synthetic route A. Reagents and conditions: a) acetone, concd H2SO4 (cat.), 6 h, 86%; b) Deoxo-fluor™, DCM, 40 °C, 30 min, 84%; c)
NaBH4, ethanol, 0 °C, 2 h, 65%; d) DIBAL-H, toluene, 40 °C, 64%; e) CH2[P(O)(OMe)2]2, DCM, 50% aq NaOH, 60%.
Scheme 3: Synthetic route B. Reagents and conditions: a) acetone, concd H2SO4 (cat.), 4 h, 90%; b) TrCl, pyridine, DMAP, rt, 16 h, 94%; c)
CH2[P(O)(OMe)2]2, 50% aq NaOH; DCM, 64%; d) anhyd ZnCl2, DCM, rt, 2 h, 78–81%; e) TsF, TBAF, THF, reflux, 16 h, 83–92%; f) i) TMSBr, DCM,
rt; ii) TFA:H2O (1:1), iii) cyclohexylamine, pH ~11, 84–87%; g) i) TMSBr, DCM, rt; ii) TFA:H2O (1:1), iii) Ac2O, pyridine, 16 h, 40–47%.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 37.
Figure 2: X-Ray crystal structure of cyclohexylammonium salt 8a.
chromatographic separation of the initial product mixture (α:β spectra were recorded on Nicolet Avatar 360 FT-IR. High resol-
of 4:1). Detritylation of 21a, b was accomplished with ZnCl2 ution mass spectrometry (HRMS) was carried out using a
[9] to generate the 5-hydroxyphosphonates 22a and 22b in a Micromass LCT (Manchester, UK) mass spectrometer with
good yield. The free alcohol of both epimers was then fluorin- electrospray ionization (ESI) operating in positive and negative
ated at the 5-position using tosylfluoride and TBAF in refluxing modes. Optical rotations were measured on Perkin-Elmer model
THF [10,11]. Sequential deprotection of 23a and 23b with 341 polarimeter.
TMSBr and then TFA yielded the free phosphonic acids which
were neutralised with cyclohexylamine [12] to generate the 5-Deoxy-5-fluoro-2,3-O-isopropylidene-D-ribono-1,4-lactone
non-hygroscopic salts 8a, b and 9a, b which could be recrystal- (15). Deoxo-Fluor™ (3.06 cm3, 16.58 mmol) was slowly added
lised from MeOH/acetone. X-Ray structure analysis of a suit- to a stirred solution of 2,3-O-isopropylidene-D-ribono-1,4-
able crystal of the fluoromethyl phosphonate 8a was obtained lactone 14 [5] (1.04 g, 5.53 mmol) in DCM (10 cm3) at ambient
(Figure 2) which confirmed its structure and stereochemical temperature. After stirring at 40 °C for 30 min, the reaction
relationship to intermediate ribose-1-phosphate metabolite 5. mixture was cooled down to ambient temperature and silica gel
Clearly, phosphonate 8a formed a 1:1 salt with the amine. Addi- (0.5 g) was carefully added. After removal of solvent, silica gel
tionally, 23a and 22a were treated in separate reactions with was applied to a silica gel column eluting with EtOAc:hexane
acetic anhydride in dry pyridine [13] to generate the cyclic (1:3) to afford 15 as a white solid (0.88 g, 84%); mp: 60–62 °C;
phostones 10 and 11 respectively. In each case this conversion [α]20D: −82.8° (c 5.0 × 10−3, CHCl3); 1H NMR (400 MHz;
could be conveniently followed by a change in the 31P-NMR CDCl3): δ = 1.39 (s, 3H, CH3), 1.48 (s, 3H, CH3), 4.67 (ddd,
resonance of 27 ppm (phosphonate) to 44 ppm, characteristic of 1H, 3JHH = 1.9, 2JHH = 11.0, 2JHF = 46.1, H-5), 4.72 (dddd, 1H,
a cyclic phostone. Purification by chromatography allowed the 3JHH = 1.7, 3JHH = 1.7, 3JHH = 1.7, 3JHF = 34.57, H-4), 4.74
recovery of the phostones 10 and 11 in moderate yield.
(ddd, 1H, 3JHH = 1.8, 2JHH = 11.0, 2JHF = 48.1, H-5), 4.81 (dd,
1H, 3JHH = 3.3, 3JHH = 5.6, H-3), 4.85 (d, 1H, 3JHH = 5.7, H-2).
Incubation of the phosphonate salts 8a and 9a with the S. 13C NMR (100 MHz; CDCl3): δ = 25.5 (CH3), 26.8 (CH3), 75.1
cattleya PNP did not result in an inhibitory effect, and clearly (d, 4JCF = 3.9, C-2), 77.2 (d, 3JCF = 5.1, C-3), 80.3 (d, 2JCF =
the phosphonates are not good substrate analogues of the phos- 19.2, C-4), 82.2 (d, 1JCF = 171.3, C-5), 113.9 (C(CH3)2), 173.6
phates with this enzyme. We are currently exploring phosphon- (C-1). 19F NMR (282 MHz, CDCl3): δ = −236.0 (ddd, 3JHF =
ates 8a and 9a as inhibitors of the isomerase, the next enzyme 3.3, 2JHF = 34.8, 2JHF = 46.3). νmax (KBr): 3563, 2993, 1804,
on the pathway, and in order to probe the molecular mechanism 1455, 1384, 1272, 1054, 849, 610, 513. HRMS (ES+): Calcd.
of this enzyme, these phosphonates and the phostones 10 and 11 for C8H11FO4Na [M+Na]+: 213.0539, found: 213.0537.
are being used in co-crystallisation trials with each of the over-
expressed enzymes (PNP and isomerase).
5-Deoxy-5-fluoro-2,3-O-isopropylidene-D-ribofuranose (17).
A solution of DIBAL-H (1 M in hexane, 2.20 ml, 2.18 mmol)
was carefully added to a solution of 5-deoxy-5-fluoro-2,3-O-
Experimental
Nuclear magnetic resonance (NMR) spectra were obtained isopropylidene-D-ribono-1,4-lactone (15) (0.42 g, 2.18 mmol)
using Bruker Advance 300 and Bruker Advance II 400. All in dry toluene (10 ml) at 40 °C and the reaction was monitored
chemical shifts (δ) are reported in parts per million (ppm) and by 19F NMR. After completion, MeOH (2 ml) was added. The
coupling constants (J) are given in Hertz (Hz). Melting points slurry gel was broken by adding sat. aq. solution of sodium
were determined in Pyrex capillaries using a Gallenkamp potassium tartrate (1 ml). After extracted into ether (3 × 10 ml),
Griffin MPA350.BM2.5 melting point apparatus. Infra red (IR) the combined organic phases were washed with brine and dried
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Beilstein Journal of Organic Chemistry 2009, 5, No. 37.
over MgSO4. After removal of solvent under reduced pressure (15 ml) and then the reaction mixture was brought to reflux.
the residue was purified over silica gel eluting with 60% After refluxing for 18 h, the reaction mixture was cooled down
EtOAc/hexane to afford 17 as colourless oil (0.26 g, α/β = 7.6/1, to ambient temperature and then filtered through a shot pad of
63.6%) and 16 (25.4 mg, 6.0%). α-anomer: 1H NMR (300 silica gel washing with EtOAc. After removal of solvent the
MHz; CDCl3): δ = 1.27 (s, CH3), 1.43 (s, CH3), 3.27 (t, 3JHH = residue was purified over silica gel eluting with MeOH:DCM
5.17, -OH), 4.31–4.41 (m, 2H, H-4, H-5, (overlap with β, H-4, (1:20) to afford 23a as colourless oil (0.148 g, 92.3%). [α]D20:
H-5)), 4.44–4.61 (m, 2H, H-3, H-5 (overlap with β, H-3, H-5)), −16.44° (c 2.25 × 10−3, CHCl3). 1H NMR (300 MHz; CDCl3):
4.71 (d, 3JHH = 5.9, H-2), 5.38 (dd, 1H, 3JHH = 2.5, 3JHH = 5.3, δ = 1.28 (s, 3H, C(CH3)2). 1.42 (s, 3H, C(CH3)2), 2.13 (ddd,
H-1). 13C NMR (75 MHz; CDCl3): δ = 24.9 (CH3), 26.5 (CH3), 1H, 3JHH = 6.7, 2JHH = 15.4, 2JHP = 18.1, H-1), 2.23 (ddd, 1H,
81.2 (d, 3JCF = 5.5, C-4), 82.2 (d, 1J = 171.3, C-5), 84.8 (C-3 or 3JHH = 6.6, 2JHH = 15.4, 2JHP = 18.4, H-1), 3.68 (d, 3H, 3JHH =
C-2), 86.1 (C-2 or C-3), 103.3 (C-1), 112.7 (C(CH3)2). 19F 3.9, POCH3), 3.70 (d, 3H, 3JHH = 3.9, POCH3), 4.12 (ddd, 1H,
NMR (282 MHz, CDCl3): δ = −230.8 (dddd, 4JHF = 3.3, 3JHF = 3JHH = 2.9, 3JHH = 2.9, 3JHF = 33.1, H-5), 4.26 (dddd, 1H, 3JHH
37.5, 2JHF = 47.3, 2JHF = 47.3, 1F). β-anomer: 1H NMR (300 = 3.2, 3JHH = 6.6, 3JHH = 6.6, 3JHP = 10.3, H-2), 4.44 (ddd, 1H,
MHz; CDCl3): δ = 1.50 (s, CH3), 1.33 (s, CH3), 3.93 (d, 3JHH = 3JHH = 3.4, 2JHH = 10.2, 2JHF = 46.8, H-5), 4.48 (ddd, 1H, 3JHH
10.9, -OH), 4.31–4.41 (m, 2H, H-4, H-5, (overlap with α, H-4, = 3.2, 2JHH = 10.2, 2JHF = 47.6, H-5), 4.65 (dd, 3JHH = 3.9,
H-5)), 4.44–4.61 (m, 2H, H-3, H-5 (overlap with α, H-3, H-5)), 3JHH = 6.0, 1H, H-3), 4.77 (d, 3JHH = 6.0, 1H, H-4). 13C NMR
4.74 (ddd, 1H, 3JHH = 0.8, 3JHH = 1.5, 3JHH = 6.4, H-4), 5.33 (75 MHz; CDCl3): δ = 24.9 (CH3), 25.5 (d, 2JPC = 141.9, C-1),
(ddd, 1H, 3JHH = 3.7, 3JHH = 3.7, 3JHH = 10.9, H-1). 13C NMR 26.2 (CH3), 52.3 (d, 2JPC = 6.4, POCH3), 52.6 (d, 2JPC = 6.2,
(75 MHz; CDCl3): δ = 24.7 (CH3), 26.1 (CH3), 79.5 (C-2), 79.6 POCH3), 76.9 (d, 2JCF = 1.9, C-2), 81.7 (d, 2JPC = 7.5, C-3),
(d, 2JCF = 17.8, C-4), 80.7 (d, 3JCF = 6.7, C-3), 85.1 (d, 1J = 82.1 (d, 2JCF = 6.4, C-4), 82.5 (d, 2JCF = 17.8, C-5), 84.8 (d,
170.5, C-5), 97.7 (C-1), 114.2 (C(CH3)2). 19F NMR (282 MHz, 1JCF = 172.4, C-6), 112.7 (C(CH3)2). 31P NMR (121 MHz;
CDCl3): δ = −225.4 (dddd, 4JHF = 3.2, 3JHF = 23.1, 2JHF = CDCl3): δ = 31.65–32.38 (m, P). 19F NMR (282 MHz; CDCl3)
46.5, 2JHF = 46.5, 1F). νmax (neat): 3426, 2944, 1376, 1211, −229.3 (ddd, 3JHF = 2.2, 3JHF = 33.2, 2JHF = 33.2, 2JHF = 47.1,
1072, 868, 504. HRMS (ES+): Calcd. for C8H13FO4Na 1F). νmax (neat): 2954, 1372, 1209, 1025, 819, 503. HRMS
[M+Na]+: 215.0696, found: 215.0691.
(ES+): Calcd. for C11H20O4FPNa [M+Na]+: 321.0879, found:
321.0879.
D-allo,altro-2,5-Anhydro-1-deoxy-1-(dimethoxyphosphinyl)-
6-fluoro-3,4-O-isopropylidenehexitol (18). 50% aq Solution D-allo-2,5-Anhydro-1-deoxy-1-(dimethoxyphosphinyl)-6-
NaOH (3 ml) was slowly added to a vigorously stirring mixture fluoro-3,4-O-isopropylidenehexitol (23b). The same
of 5-deoxy-5-fluoro-2,3-O-isopropylidene-D-ribofuranose 17 procedure as described for 23a was repeated with 22b (70 mg,
(0.125 g, 0.63 mmol) and tetramethyl methylenediphosphonate 0.23 mmol) to afford 23b as a colourless oil (60 mg, 83.1%).
(0.16 g, 0.69 mmol) in DCM (3 ml) at ambient temperature. [α]D20: −18.78° (c 2.45 × 10−3, CHCl3), 1H NMR (300 MHz;
After 18 h, the reaction mixture was diluted with DCM (10 ml) CDCl3): δ = 4.64 (dd, 3JHH = 3.9, 3JHH = 6.6, 1H, H-4), 4.49
and the aq phase was extracted with DCM (2 × 10 ml). The (ddd, 1H, 3JHH = 2.8, 2JHH = 10.4, 2JHF = 47.6, H-6), 4.48 (dd,
combined organic phases were dried over MgSO4, and filtered. 1H, 3JHH = 4.3, 3JHH = 6.6, H-3), 4.45 (ddd, 1H, 3JHH = 3.5,
After removal of solvent, the residue was purified over silica 2JHH = 10.8, 2JHF = 47.0, H-6), 4.23 (dddd, 1H, 3JHH = 4.2,
gel eluting with 5% MeOH:DCM to afford a mixture of epimers 3JHH = 6.7, 3JHH = 6.7, 3JHP = 11.1, H-2), 4.09 (ddd, 1H, 3JHH
18 as colourless oil (0.11 g, α/β = 3.2/1, 58.5%).1H NMR (400 = 3.4, 3JHH = 3.4, 2JHF = 28.3, H-5), 3.71 (d, 3H, 3JHH = 2.2,
MHz; CDCl3): δ = 1.19 (C(CH3)2), 1.33 (C(CH3)2), 1.95–2.20 POCH3), 3.67 (d, 3H, 3JHH = 2.3, POCH3), 2.09 (d, 1H, 2JHP =
(m, 2H, H-1), 3.58–3.63 (m, POCH3), 3.95–4.69 (m, 6H). 13C 18.4, H-1), 2.13 (dd, 1H, 3JHH = 0.9, 2JHP = 18.4, H-1), 1.47 (s,
NMR (162 MHz; CDCl3): δ = 30.3–31.1 (m, Pα), 31.7–32.4 (m, 3H, C(CH3)2), 1.28 (s, 3H, C(CH3)2). 13C NMR (75 MHz;
Pβ). 19F NMR (282 MHz, CDCl3): δ = −231.1 (ddd, 3J = 28.90, CDCl3): δ = 25.9 (CH3), 27.7 (CH3), 30.1 (d, 2JCP = 141.1,
2J = 47.32, 2J = 47.32, 1Fα), −229.3 (dddd, 4J = 2.26, 3J = C-1), 52.7 (d, 2JCP = 6.5, OCH3), 52.9 (d, 2JCP = 6.5, OCH3),
32.94, 2J = 47.29, 2J = 47.29, 1Fβ). νmax (neat): 3466, 2955, 80.5 (d, 2JCF = 3.4, C-2), 81.2 (d, 3JCF = 7.4, C-4), 83.2 (d, 2JCF
1644, 1459, 1374, 1213, 1023, 822, 537. HRMS (ES+): Calcd. = 172.7, C-6), 83.5 (d, 2JCF = 18.3, C-5), 85.7 (d, 4JCF = 11.3,
for C11H20O4FPNa [M+Na]+: 321.0879, found: 321.0874.
C-3), 114.9 (C(CH3)2). 31P NMR (162 MHz; CDCl3): δ =
30.33−31.09 (m, P). 19F NMR (282 MHz; CDCl3): δ = −231.0
D-altro-2,5-Anhydro-1-deoxy-1-(dimethoxyphosphinyl)-6- (ddd, 3JHF = 28.8, 2JHF = 47.3, 2JHF = 47.3, 1F). νmax (neat):
fluoro-3,4-O-isopropylidenehexitol (23a). A solution of TBAF 3464, 2956, 1383, 1214, 1030, 822, 513. HRMS (ES+): Calcd.
(1 M in THF, 2.16 ml, 2.16 mmol) was added to a mixture of for C11H20O4FPNa [M+Na]+: 321.0879, found: 321.0875.
22a (0.16 g, 0.54 mmol) and TsF (0.28g, 1.62 mmol) in THF
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Beilstein Journal of Organic Chemistry 2009, 5, No. 37.
Cyclohexylammonium salt 8a. TMSBr (0.18 ml, 1.36 mmol) 32.8 (2 × C, clohexyl), 35.9 (d, 1JCP = 127.0, C-1), 51.4 (C-1,
was added to a solution of 23a (94.8 mg, 0.34 mmol) in DCM cyclohexyl), 73.1 (d, 3JCF = 5.1, C-4), 77.4 (C-3), 80.7 (d, 2JCP
(5 ml). The progress of reaction was monitored by 31P NMR. = 2.6, C-2), 84.1 (d, 2JCF = 18.5, C-5), 84.3 (d, 1JCF = 170.5,
The disappearing of signal at 31.5–32.1.0 ppm indicating that C-6). 31P NMR (162 MHz; MeOH-d4): δ = 17.9 (ddd, 3JHP =
the reaction was gone completion. A solution of TFA:H2O (1:1, 3.9, 2JHP = 17.8, 2JHP = 17.8 ). 19F NMR (376 MHz; MeOH-
1 ml) was then added to the mixture. After 30 min, water (5 ml) d4): δ = −231.6 (ddd, 1F, 3JHF = 25.6, 2JHF = 47.7, 2JHF =
was added, the solvents were removed under reduced pressure. 47.7). νmax (KBr): 3436, 2937, 2561, 2012, 1618, 1454, 1389,
To this residue was added water (5 ml) and the solvent was 1051, 974. HRMS (ES+): Calcd. for C12H26NO6FP [M+H]+:
removed under reduced pressure; this was repeated until all 330.1482, found: 330.1485.
trace of TFA was gone. To this residue 5 ml of water was added
and adjusted to pH 11 with cyclohexylamine. After removal of Fluoromethylphostone 10
solvent, the residue was dissolved in EtOH and about 0.5 Deprotection as described for 8a was repeated with 23a (80 mg,
volume of acetone was added. The precipitate was filtered off to 0.27 mmol) in DCM (5 ml). Without addition of cyclo-
afford 8a as colourless needles (97.6 mg, 87.2%). Mp. 168–170 hexylamine, the residue was dissolved in dry pyridine (1 ml)
°C, [α]D20: +18.67° (c 1.50 × 10−3, MeOH), 1H NMR (400 and acetic anhydride (0.04 ml, 0.4 mmol) was then added. The
MHz; MeOH-d4): δ = 1.07–1.16 (m, 1H, cyclohexyl), emergence of an 31P-NMR signal at 45 ppm and a disappear-
1.19–1.34 (m, 4H, cyclohexyl), 1.57–1.64 (m, 1H, cyclohexyl), ance of signal at 27 ppm indicated that the reaction had gone
1.70–1.79 (m, 2H, cyclohexyl), 1.88–1.94 (m, 2H, cyclohexyl), completion. After removal of the solvent under reduced pres-
1.87 (ddd, 1H, 3JHH = 4.9, 2JHH = 10.1, 2JHP = 19.1, H-1), 2.04 sure, the crude was purified over silica gel eluting with
(ddd, 1H, 3JHH = 10.1, 2JHH = 14.2, 2JHP = 17.1, H-1), MeOH:DCM (3:2) to afford 10 as white solid (23 mg, 40.2%).
2.91–2.98 (m, 1H, H-1, cyclohexyl), 3.83 (dddd, 1H, 3JHH = Mp. 180−182 °C, [α]D20: +103.0° (c 1.0 × 10−3, MeOH). 1H
2.0, 3JHH = 4.6, 3JHH = 8.7, 3JHF = 25.5, H-5), 4.01 (dd, 1H, NMR (300 MHz; MeOH-d4): δ = 1.73–1.98 (m, 2H, H-1), 4.25
3JHH = 4.6, 3JHH = 8.7, H-4), 4.10–4.14 (br, 1H, H-3), 4.17 (dddd, 1H, 3JHH = 2.10, 3JHH = 3.90, 3JHH = 8.30, 3JHF =
(dddd, 1H, 3JHH = 2.9, 3JHH = 4.5, 3JHH = 4.5, 3JHP = 9.7, 26.32, H-1, H-5), 4.36 (ddd, 1H, 3JHH = 3.90, 2JHH = 10.63,
H-2), 4.34 (ddd, 1H, 3JHH = 4.7, 2JHH = 10.3, 2JHF = 47.7, 2JHF = 47.18, H-6), 4.48 (ddd, 1H, 3JHH = 2.10, 2JHH = 10.63,
H-6), 4.56 (ddd, 1H, 3JHH = 2.1, 2JHH = 10.3, 2JHF = 48.4, 2JHF = 48.14, H-6), 4.67–4.71 (m, 1H, H-3), 4.72–4.82 (m, 1H,
H-6). 13C NMR (100 MHz; MeOH-d4): δ = 25.4 (2 × C, cyclo- H-2), 4.88 (ddd, 1H, 3JHH = 1.91, 3JHH = 4.61, 3JHP = 8.34,
hexyl), 25.9 (C, cyclohexyl), 31.2 (d, 1JCP = 129.5, C-1), 31.9 H-4). 13C NMR (75 MHz; MeOH-d4): δ = 29.6 (d, 1JCP =
(2 × C, cyclohexyl), 51.5 (C-1, cyclohexyl), 72.9 (d, 3JCF = 7.9, 119.5, C-1), 74.4 (d, 4JCF = 7.15, C-4), 77.8 (d, 4JCF = 8.8,
C-4), 73.4 (C-3), 79.7 (d, 2JCP = 2.7, C-2), 81.0 (d, 2JCF = 17.6, C-3), 79.5 (d, 3JCF = 18.36, C-5), 81.2 (d, 2JCP = 4.0, C-2), 83.2
C-5), 84.3 (d, 1JCF = 170.9, C-6). 31P NMR (162 MHz; MeOH- (d, 1JCF = 172.1, C-6). 19F NMR (282 MHz; MeOH-d4): δ =
d4): δ = 18.7 (ddd, 3JHP = 2.9, 2JHP = 18.1, 2JHP = 18.1 ). 19F −234.3 (ddd, 1F, 3JHF = 26.4, 2JHF = 47.4, 2JHF = 47.7). 31P
NMR (376 MHz; MeOH-d4): δ = −232.4 (ddd, 3JHF = 25.5, NMR (162 MHz; MeOH-d4): δ = 41.9–42.6 (br, m). νmax
2JHF = 47.4, 2JHF = 47.4, 1F). νmax (KBr): 3199, 2939, 2720, (PTFE): 3419, 1214, 1154, 799, 503. HRMS (ES-): Calcd. for
2012, 1597, 1429, 1389, 1121, 1018, 925. HRMS (ES+): Calcd. C6H9FO5P [M-H]: 211.0172, found: 211.0166.
for C12H26NO6FP [M+H]+: 330.1482, found: 330.1492.
Supporting Information
Cyclohexylammonium salt 8b. The same procedure as
described for preparation of 8a was repeated with 23b (53.1 mg,
The experimental and analytical data for compounds 9b,
0.19 mmol) to afford 8b as white solid (52.1 mg, 83.3%). Mp.
11, 14, 16, and 19–22 are provided in the supporting
146–148 °C, [α]D20: +3.09° (c 3.55 × 10−3, MeOH), 1H NMR
information.
(400 MHz; MeOH-d4): δ = 1.05–1.32 (m, 5H, cyclohexyl),
Supporting Information File 1
Experimental.
1.54–1.74 (m, 5H, 1H-1 overlap with 4H-cyclohexyl),
1.87–1.90 (m, 2H, cyclohexyl), 1.99 (ddd, 1H, 3JHH = 3.7, 2JHH
= 14.1, 2JHP = 18.8, H-1), 2.83–2.91 (m, 1H, H-1, cyclohexyl),
3.96 (t, 3JHH = 6.3, H-3), 3.83 (dddd, 1H, 3JHH = 3.7, 3JHH =
3.7, 3JHH = 3.7, 3JHF = 25.9, H-5), 3.97 (dd, 1H, 3JHH = 3.9,
3JHH = 5.5, H-4), 3.95–4.01 (m, 1H, H-2), 4.31 (ddd, 1H, 3JHH
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-5-37-S1.doc]
= 4.1, 2JHH = 10.2, 2JHF = 47.4, H-6), 4.36 (ddd, 1H, 3JHH = Acknowledgments
3.2, 2JHH = 10.2, 2JHF = 47.9, H-6). 13C NMR (100 MHz; Pitak Nasomjai acknowledges a Royal Thailand Goverment
MeOH-d4): δ = 25.5 (2 × C, clohexyl), 26.1 (C, cyclohexyl), Postgraduate Scholarship.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 37.
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