Enantioselective synthesis of diethyl 1-hydroxyalkylphosphonates via oxazaborolidine catalyzed borane reduction of diethyl α-ketophosphonates

Tehnhehm Asymmehy Vol. 5, No. 10. pp. 19654972, 1994 Copyright 8 1994 HsevicrscietlceLtd Primedin GreatBritain.All rightsreserved 0957-mw94 $7.oc+o.00

0957-4166(94)00277-O

Enantioselective Synthesis of Diethyl l-Hydroxyalkylphosphonates

via Oxazaborolidine Catalyzed

Borane Reduction of Diethyl ar-Ketophosphonates Tadeusz Gqjda

Instituteof Organic Chemistry, TdmkaJ University(Polite&nika), kirki

36.90-924

Lode, Poland

Abstract: Reduction of diethyl or-ketophosphonates 1 with borane and B-butyloxazaborolidine 2 as catalyst afforded diethyl (S)- or (R)-1-hydroxyalkylphosphonates 3a-d or 3e-f respectively in good yields and moderate to good enantiomeric excess (53-83 ee%). Respective diethyl (R)- and (S)-l-aminoalkylphosphonates 6 were obtained in a one-pot transformation, by the Mitsunobu reaction of lhydroxyphosphonates 3 with hydrazoic acid, and subsequent treatment of the intermediate azides 4, with triphenylphosphine, followed by hydrolysis df the iminophosphoranes 5 with water.

During the past decade the chiral 1-hydroxyalkylphosphonam have received considerable attention in organic and bioorganic

chemistry

not only as convenient

substrates for the enantioselective synthesis of l-

aminoalkylphosphonates’ but also as compounds of potential biological activity.’ Despite this, there is only limited number of synthetic approaches to optically active ar-hydroxyphosphonates with one stereogenic center and there still exists a need for new methods which would be simple and general. So far the optically active cw-hydroxyphosphonates have been obtained by the following methods: (i) chemical’% 3 and enzymatic4 resolution

of the racemic cr-hydroxyphosphonates or their derivatives, (ii) stereoselective cleavage of

homochiral dioxane acetals with triethyl phosphite,lb (iii) enantioselective addition of dialkyl phosphites to aromatic aldehydes in the presence of chiral catalyst~,~ and (iv) asymmetric addition of chiral phosphorus nucleophiles to aldehydes.6 To the best of my knowledge, however, catalytic enantioselective reduction of a-ketophosphonates has not been developed.’ I wish to report herein a simple enantiocontrolled route to chiral 1-hydroxyalkylphosphonates which takes advantage of a development in the enantioselective reduction of prochiral ketones to chiral alcohols by means of catalytic amounts of oxazaborolidines with borane as a reductant.* Starting diethyl cr-ketophosphonates 1 were obtained from triethyl phosphite and acyl or benzoyl chloride respectively.g According to the Scheme 1, reduction was accomplished by treatment of diethyl acyloxyphosphonate 1 and catalytic amount (5 mol%) of freshly prepared B-butyloxazaborolidine” (S)-2a or (R)-2b respectively in anhydrous tetrahydrofuran with 0.9 equiv. of borane - THF complex. The reaction was completed within 2 h at 26 - 28 “C, and afforded, after usual work up or subsequent distillation in VUCKO, the appropriate diethyl 1-hydroxyalkylphosphonates 3 in good (53-85%) yields. The best enantioselectivity was 1965

1966

T. GAJDA

achieved, using 5 mol 56 of catalyst 2. The structure of hydroxyphosphouates 3 was confirmed by 31P-NMR and ‘H-NMR spectroscopy. The results are summ~i~

1

in Table 1.

@I-* (RI-=

la RI=

3a Rl=Et,R2=Cti,R3=H

Et

IbR’=Bu

3b R1=Bu,Rz=OH,R3=H

lcR’=i%u ldR’=Ph

3d R4 =Ph,R2=OH,R3=H

3c R~=CBU,R~=OH,R~=H 3e Rf=Et,R2=H,R3=OH 3f R1=iBu,R2=H,R3=OH

Scheme 1 1 in the presence of chiral catalyst (9.28

Table 1. Enantiose&zctive reduction of diethyl ~-ke~h~p~~~ or (R)-2b and borane. Ketone

Entry

1

I

2

Catalyst

Product

Yield

1

(5 moI%)

3

(%I

18

(s)-28

3a

56

lb

I

1

(Sk28

1

3b

1

60

[cr]g2

E.e( %jb

Config.

79

s

+12.13”

S

1 +14.63”

1

82

1

J

3

1C

(q-28

3c

60

83

S

4

Id

(s)-28

3d

85

53

S

5

18

(R)-2b

3e

61

77

R

-11.91”

6

lb

(R)-2b

3f

53

83

R

-17.W’

1

+ 18.26”

-16.57d*F

I a Yield of isolated, pure product based on 1; b firming by 31P-NMR (2OOMHz) analysis of the corresponding (R)- Masher ester;’ Measured in CH,OH; d Measured in CHCI,; e Litsd [cY]~~=-6.6(CHCl,), ee=20%, config.: S.; ’ Lit.lb [cy]: = -16.5 (CHCI,), ee>95%, config.: R. As can be seen from the Table 1, the diethyl 1-hydroxyalkylphosphonates

3 were obtained with predictable

stereochemistry and in moderate to good euantiomeric excess (53-83 ee%). The enantiomeric excess of (Yhydrox~h~phoM~ (+)-MTPA-Cl;

3 has been estimated by 3’P-NMR aualysis %*” of their Masher eaters (derived from {S)-

the value of 3’P-NMR nonequivalence between the respective diastereoisomers is in the range

A6= 0.37 - 0.48 ppm). The observed stereochemistry of the reduction is in accordance with the mechanism

1967

Diethyl 1-hydroxyalkylphosphonates

proposed for ketones by Corey et al.” Thus, applying (S)-2a oxazaborolidine as catalyst, the diethyl (S)-lhydroxyalkylphosphonates 3a-d were enantioselectively obtained (Entry l-4). whereas for (R)-2b catalyst, the (R)- enantiomers of 3 were afforded (Entry 5, 6). Generally enantiomeric excesses of the cu-hydroxyphosphonates 3 obtained, are lower than that observed for secondary chiral aIcohols.i2 Higher values of enantiomeric excesses were achieved for aliphatic than for phenyl analogues of o-ketophosphonates 1 (Entry l-3,5,

6 vs.

4 respectively), probably because of comparable steric demands for phosphoryl and phenyl group flanking the carbonyl group in the last case. The absolute configuration of diethyl 1-hydroxyalkylphosphonates 3 was assigned by correlation with ol-hydroxyphosphonates of known configuration,‘b*“~k.d and eventually confirmed by chemical correlation with known ar-aminophosphonates (Mitsunobu reaction, vide i@u). Recently

we have devised

a simple

methodology

hydroxyphosphonatesi3 and or-hydroxyphosphinates”

for a one-pot

transformation

of racemic

into the respective ar-aminoderivatives

necessity of isolation of the intermediate azides. In continuation

o-

without the

of these studies herein I report the

applicability of this strategy to a one-pot transformation of optically active diethyl 1-hydroxyalkylphosphonates 3 to diethyl I-aminoalkylphosphonates

6. A key step of this transformation, the Mitsunobu azidation, has been

unequivocally proved to occur in the &2 manner for chiral secondary alcohoW5 and dialkyl cr-hydroxyphosphonates . ’

% 1

OH R

;(OEt), 0

i

RAP(OEtJ2

‘$‘2

5

2

R-P(OEt), 8

8

[

4a-d

3a-d

6a-d

Sa-d

3-6

a

t e

Et Bu i-Bu Ph Et

f

1 I-Bu

b

I. Y. iii RdP(OEt),

-

R

ii

8

3e-f

-gents

R’

6e-f

andconditior!s: 1, P~P/Et0,C+l=M02EUHhg, CH&, -lO%to r.t. m; ii, P~Phenzene, rl., 2h; ill. H# 5065% 5h.

Scheme 2

According to the Scheme 2, diethyl I-axidoalkylphosphonates 4 were prepared by the interaction of optically active diethyl 1-hydroxyalkylphosphonates 3 with the preformed betaine type adduct of triphenylphosphine diethyl azodicarboxylate - hydrazoic acid under the Mitsunobu conditions. The azides 4 thus formed were converted in siru by the Staudinger reaction’6 with triphenylphcsphine into the respective iminophosphoranes

1968

T. GAIDA

5, subsequently hydrolysed with water directly to the corresponding diethyl 1-aminoalkylphosphona@ good overall yield (SO-88W) and purity. The structure of the diethyl 1-aminoalkylphosphonates

6 in

was confiied

by 3LP-NMR and ‘H-NMR spectroscopy. The results are summarized in Table 2. Table 2. Enantioselective

synthesis of diethyl 1-aminoalkylphosphonates

Alcohol

Product

Yield

3

6

(46)

1

3a

6a

2

3b

3

6.

E.e( %)b

Config.

60

76

R

-6.W

6b

88

80

R

-10.99

3c

6c

74

82

R

-18.65%

4

3d

6d

67d

48

R

-1.62’

5

3e

6e

50

76

S

+6.33’

6

3f

6f

71

82

S

+ 17.42g

Entry

r&Y c

I ’ Yield of isolated, pure product based on 3; b E.e evaluated by 31P-NMR (200 MHz) spectroscopy of the amides obtained by reaction of camp. 6 with (S)-( +)-MTPA-Cl (A&= 0.08-o. 1 ppm); ’ Measured in CHCI,; d Isolated as hydrochloride; ’ Lit.‘” [a&,= 5.89 (CHCl,), ee=82%, config.: S; Lit.‘% [rw]n=7.18(CHCI,), opt. pure, config.: S; f Measured in H,O; Lit.‘7c [orIn=-2.4(H,O), ee=70%, config.: R; g Lit.lb [0~1~=18_4(CHCl~), ee>95%, config.: S. Thus (R)-aminophosphonates enantiomers

6e-f

6a-d were formed from (S)-ar-hydroxyphosphonates

were obtained from (R)-ar-hydroxyphosphonates

excesses close to those of the corresponding aminoalkylphosphonates

6a-f

chemical correlation above mentioned

the configuration

strategy

3e-f (Entry 5, 6), with enantiomeric

starting materials. Absolute configuration

was assigned

configuration.‘b* I**,I7 In all cases complete

3a-d (Entry l-4), and (S)-

by

inversion

correlation

with

of configuration

cr-aminophosphonates was observed,

of the starting cu-hydroxyphosphonates

for the enantioselective

of the diethyl lof

known

thus confirming

3, and also the usefulness

by

of the

syntheses of cY-aminophosphonates.‘8

In summary, the described oxazaborolidine catalyzed reduction of cw-ketophosphonates with borane offers a new and simple route to enantioselective good

enantiomeric

excess

synthesis of diethyl 1-hydroxyalkylphosphonates

and determined

stereochemistry.

Additionally,

stereocontrolled one-pot transformation of optically active diethyl l-hydroxyalkylphosphonates, alternative for the enantioselective synthesis of a-aminophosphonates Further investigation on oxazaborolidine

with moderate to

it was documented

that

may be useful

proposed recently.‘s

catalyzed enantioselective reduction of /3- and y-ketophosphonates

and phosphinates are currently under way and will be reported in due course. Experimental

3LP-NMR spectra were recorded on a Bruker AC 200 and Bruker AM 500 spectrometers operating at 81 and

Diethyl I-hydroxyaikylphosphonates

1969

202 MHz respectively. Positive chemical shifts are downfield from ext. H,PO,. ‘H-NMR spectra were recorded on a Bruker AC 200 spectrometer operating at 200 MHz ( CDCI, soln./TMS ht.). Optical rotations were measured in 1 dm cell on a Horiba polarimeter. FABIMS were recorded on a APO Electron (Ukraine) Model1 MI 12OOlE mass spectrometer equipped with a FAB ion source (thioglycerol matrix). Melting points were determined in open capillaries and are uncorrected. THF was dried by distillation from lithium aluminum hydride.

(S)-(+)-cu-methoxy-cY-trifluoromethylphenylacetyl

chloride (MTPA-Cl,

Fluka) was used for

derivatization of hydroxyphosphonates and aminophosphonates. Mosher‘s esters and amides were prepared according to the described procedure” (crude products were analyzed). Diethyl azodicarboxylate (DEAD) was obtained by established procedure. I9 Diethyl cy-ketophosphonates were prepared according to the literature from triethyl phosphite and acyl or benzoyl chloride.’ (S)- and (R)-5,5-diphenyl-2-butyl-3,4-propano-1,3,2oxazaborolidine (Corey‘s reagent) were prepared according to the literature’o from butylboronic acid and (S)or (R)-2-(diphenylhydroxymethyl)pyrrolidine

respectively, just prior to use in THF solution.

Diethyl l-hydroxyalkylphasphonates 3sf. Gent~ufprocedure. 1M Borane-THF complex (0.9 eq., 9 mL) was slowly added via syringe within 30 min. and under argon to a stirred solution of diethyl ar-ketophosphonate 1 (0.01 mol) and B-butyloxazaborolidine 2 (O.O16g, 5 mol%) in dry THF (6 mL) at 2628°C. After stirring for 2 h at 26°C the reaction mixture was cooled to 0°C and 3.5M solution of dry HCl in methanol (5 mL) was added to the solution. The solvent was removed under reduced pressure, and the residue was ccevaporated

with benzene (3x20 mL). Ether (40 mL) was added to the semi-solid residue. The

precipitated 2-(diphenylhydroxymethyl)pyrrohdine

hydrochloride was filtered off, and the filtrate was

evaporated under reduced pressure. The oily residue was dissolved in CH,CI, (80 mL), the solution was successively washed with 5% aq. HCI (2x1 mL), water (1 mL), aq. NaHC4

(1 mL), and water (2 mL),

dried (MgSO,) and concentrated under reduced pressure.The volatile materials were removed at 45WO. 1 Torr or the crude product was distilled ix vucuo to afford analytically pure diethyl 1-hydroxyalkylphosphonate 3. Diethyl l-hydroxypropylphosphomte3a;

yield: 5696, colorless oil, b.p. 112-l 14W0.4 Torr, ni” = 1.4367;

3’P-NMR (CDCI,): 6 = 26.01 ppm.; ‘H-NMR: 6 = 1.05 (t, 3H, J = 7.36 Hz, CH3, 1.31 (t, 6H, J = 7.06 Hz, 2CH,), 1.57-1.90 (m, 2H, CH,), 3.29 (bs, lH, OH), 3.75 (dt, lH, J = 4.29, 9.49 Hz, CH), 4.07-4.22 (m, 4H, 2CH,); FAB/MS: m/z(%): 197(MH+,lOO), 121(22), 93(51), 69(63), 59(33); Elemental analysis(%); C,H,,O.,P calcd.: C: 42.85, H: 8.74; found: C: 42.71, H: 8.60. Diethyl l-hydroxypentylphosphonate3b: yield: 60%. colorless oil, b.p. 114-l 18W0.4 Torr, ni” = 1.4385, 3’P-NMR (CDCI,): S = 26.11 ppm.; ‘H-NMR: 6 = 0.89 (bt, 3H, J = 6.85 Hz, CH,), 1.32 (t, 3H, J = 7.04 Hz, 2CH3, 1.28-1.80 (m, 6H, 3CH,), 3.18 (bs, lH, OH), 3.83 (dt, lH, J = 4.42, 9.02 Hz, CH), 4.07-4.22 (m, 4H, 2CH,); FAB/MS: m/z(%): 225(MH+,lOO), 121(33), 93(%), 87(15), 83(52), 65(71); Elemental analysis(%); C,H,,O,P c&d.:

C: 48.20, H: 9.44; found: C: 48.06, H: 9.31.

Diethyl 1-hydroxy3methylbutylphosphonate

3c; yield: 60%. colorless oil, b.p. 112-l 14”c/O.4 Torr, ni”

= 1.4374, 31P-NMR (CDCI,): S 7 26.56 ppm.; ‘H-NMR: 6 = 0.9 (d, 3H, J=6.54 Hz, CH,), 0.95 (d, 3H, J = 6.68 Hz, CH3, 1.32 (t, 6H, J = 7.04 Hz, 2CH,), 1.39-2.00 (m, 3H, CH, CHJ, 3.04 (bs, lH, OH),

T. GAJDA

1970

3.88-3.98 (m, lH, CH), 4.07-4.22 (m, 4H, 2CHd; FAB/MS: m/z(%): 225(MH+,51),

121(23), 93(52),

73(75); Elemental analysis(%); C,H,,O,P calcd.: C:48.20, H: 9.44; found: C: 48.11, H: 9.34. Diethyl l-hydroxy-l-phenybnethylphasphonate

22.12ppm.;

‘H-NMR:6

3e yield: 85 96, m.p. = 57-59°C; 31P-NMR (CDCI,): 6 =

= 1.21, 1.26(2t, 6H, J = 7.07Hz, 2CH3, 3.60@,

2CH,), 5.01 (d, lH, J = 10.82 Hz, CH), 7.29-7.51 (m,5H,,,&

lH,OH),

3.90-4.13(m,

4H,

FAB/Ms: m/z(%): 245(MH+,lOO), 227(26),

139(24), 121(40), 107(76), 93(21), 91(64); Elemental analysis(%); C,,H,,O,P

calcd.: C: 54.09, H: 7.08;

found: C:53.85, H: 6.91. Diethyl l-hydroxypropylphosphonate3e;

yield: 6196, colorless oil, b.p. 102-104“C/O.3 Ton; ng” = 1.4363,

31P-NMR (CDCI,): 6 = 26.04 ppm.; ‘H-NMR spectrum was identical to that of the compound 3a; FAB/MS: m/z(%): 197(MH+,38), 121(9), 93(13), 69(60), 59(14); C,H,,O,P c&d.:

C: 42.85, H: 8.74; found: C:

42.76, H: 8.67. Diethyl 1-hyclroxy-3-methylbutylphospholrPte

3C; yield: 53X, colorless oil, b.p. 124-125YYO.8 Torr, ni”

= 1.4379, “P-NMR (CDCI,): 6 = 26.48 ppm.; ‘H-NMR spectrum was identical to that of the compound 3c, FAB/MS: m/z(%): 225(MH+,lOO), 121(15), 93(40), 87(6), 83(19), 65(19); Elemental analysis(%): C,H,,O.,P calcd.: C: 48.20, H: 9.44; found: C: 48.11 H: 9.37. Diethyl 1-aminoalkylphosphonates

6sf.

General procedure. 13*I4 A solution of diethyl azodicarboxylate

(DEAD) (2.09 g, 0.012 mol) in CH,CI, (5 mL) was added dropwise with stirring and external cooling to a solution of triphenylphosphine

(3.14 g, 0.012 mol) in CH.$I, (20 mL) at -5°C. The mixture was cooled to

-10°C. and 1.85 molar solution of HN, in benzenea (0.0125 mot) was slowly added. Stirring was continued for 5 min. at o”c, and the appropriate 1-hydroxyphosphonate 3 (0.01 mol) was then added. The mixture was kept for 30 min. at o”c, and stirring was then continued for 20 h at r.t. The precipitate of ethyl 3(ethoxycarbonyl)carbazate

was filtered off, and the filtrate was evaporated under reduced pressure. The

semisolid residue was extracted with hexane (3x 50 mL). The combined extracts were evaporated in vacua. The oily residue was dissolved in benzene (15 mL) and triphenylphosphine in one portion to the solution.Stirring

(2.75 g, 0.0105 mol) was added

was continued for 2 h at r.t. Water (1.8 mL, 0.1 mol) was then added

and the mixture was heated for 5 h at 50-55°C. The mixture was cooled to r.t. and extracted with 5% aq. HCI (3x5 mL). The combined acid extracts were then reextracted with CHQ,

(3x15 mL). The acid phase was

then cooled to o”C, and the solution was made alkaline by the addition of an excess of solid K$O,.The product was extracted with CH,CI, (5x30 mL), the extracts was dried (N&SO,), and solvent was evaporated under reduced pressure. The rest of the volatile material was removed at 35YXO.02 Torr, to give pure diethyl 1-aminoalkylphosponate

6. The aminophosphonate 6d was isolated as hydrochloride.

Diethyl l-aminopropylphosphonate

6rr, yield: 60%) yellow oil, nk” = 1.4391, 31P-NMR (CDCI,): 6 = 29.8

ppm; ‘H-NMR: 6 = 1.03 (t, 3H, J = 7.4 Hz, CH,), 1.30 (t. 6H, J = 7.07 Hz, 2CH,), 1.39-1.91 (m, 4H, CH,, NH,), 2.78-2.90 (m, 1H CH), 4.04-4.20 (m, 4H, 2CH3; Elemental analysis(%); C: 43.07, H: 9.29:

found: C: 42.95, H: 9.19; oxalate: m.p.

Dkthyl l-aminopentylphosphonate

C,H,,NO,P c&d.:

108-11U’C (dec.)

6b; yield; 88 96, colorless oil, ni” = 1.4408, “‘P-NMR (CDCI,): 6 =

1971

Diethyl 1-hydroxyalkylphosphonates

29.97ppm.; ‘H-NMR: 6 = 0.88 (bt, 3H, J = 6.84 Hz, CHd, 1.30 (t, 6H, J = 7.06 Hz, 2CH3, 1.27-1.85 (m, 8H, 3CH,, NH& 2.84-2.96 (m, lH, CH), 4.014.20 (m, 4H, 2CHJ; Elemental analysis(%); w22N03P calcd.: C:48.41, H: 9.93; found: C: 48.30 , H: 9.85 ; oxalate: m.p. Diethyl l-amin~3-methylbutylpbasphon8te6e;

6 = 30.44 ppm.; ‘H-NMR: 6 = 0.87.0.93

(dec.)

(2d, 6H, J = 6.58 Hz, 2CH3), 1.31 (t, 6H, J = 7.06 Hz, 2CH,),

1.22-1.97 (m, 5H, CH,, NH,, CH), 2.94-3.07 analysis(%); C,H,NO,P

124-l=

yield: 74%. yellow oil, do = 1.4413, 3’P-NMR (CDCI,):

(m, lH,

CH), 4.04-4.19

(m, 4H, 2CH,); Elemental

calcd.: C: 48.41, H: 9.93; found: C: 48.35, H: 9.84; oxalate: m.p. 123-12X

Diethyl l-amino-l-phenylmethylpbasphonate

(dcc.)

hydrochloride 6d; yield: 67%. m.p. 157-158°C (dec.). 31P-

NMR (D,O): 6 = 18.1 ppm.; ‘H-NMR(D,O): 6 = 1.27, 1.29 (2t, 6H, J = 7.1 Hz, 2CH,), 4.03-4.22 (m, 4H, 2CH3, 4.8 (bs, NH,+), 4.95 (d, 1H. J = 17.72 Hz, CH), 7.55 (bs, 5H._);

Elemental analysis(%);

C,,H,,CINO,P calcd.: C: 47.23, H: 6.85; found: C: 47.00, H: 6.72. Diethyl l-aminopropylphosphonate

6e; yield: 50%, yellow oil, trio = 1.4414, 31P-NMR (CDCU: 6 = 29.77

ppm.; ‘H-NMR spectrum was identical to that of the compound 6a; calcd.: C: 43.07, H: 9.29: found: C: 42.96, H: 9.20 ; oxalate: m.p. Diethyl l-amino-3-methylbutylphosphonate6f:

Elemental analysis(%); C,H,,NO,P 107-108T

(dec.).

yield: 71 I. yellow oil, trio = 1.4415, 31P-NMR (CDCI,):

6 = 30.45 ppm.; ‘H-NMR spectrum was identical to that of the compound 6c: Elemental analysis(%); C,H2,N03P calcd.: C: 48.41, H: 9.93; found: C:48.23, H:9.84; oxalate: m.p. Acknowledgement:

123-124.5”c (dec.)

The author acknowledges financial support of this work by a grant PB-0428/P3/92/03

from the Committee of Scientific Researches. References:

1.

a) Hammerschmidt, F.; Vi3llenkle, H. Liebigs Ann. Chem. 1989, 577; b) Yokomatsu, T.; Shibuya, S. Tetrahedron: Asymmetty, 1992, 3, 377.

2.

Patel, D.V.; Rielly-Gauvin, K; Ryono, D.E. Tefruhedron Letf. 1990, 31, 5587; Patel, D.V.; RiellyGauvin, K; Ryono, D.E ibid 1990, 31, 5591; Stowasser, B.; Budt, K-H.; Jian-Qi, L.; Peyman, A.; Ruppert, D. ibid 1992, 33, 6625; Meier, C. Angew. Chem., ht. Ed. En@. 1993, 32, 1704.

3.

Hammerschmidt, F.; Viillenkle, H. Liebigs Ann. Chem.1986, 2053; Jacques, J.; Leclercq, M.; Brienne, M-J. Tetrahedron 1981, 37, 1727; Hoffmann, M. J. P&t.

Chem. 1990.332,251;

Sasaki, M. Agric.

Biol. Chem. 1986, 50, 741. 4.

a) Hammerschmidt, F; Li, Y-F. Tefrohedron: Asymmerry 1993, 4, 109, b) Khushi, T.: O‘Toole, K.J.; Sime, J.T. Tefrahedron Let& 1993, 34, 2375; c) Heisler, A.; Rabiller, C; Douillard, R.; Goalou, N.; Hagele, G.: Levayer, F. Tetrahedron:Asynmet~

5.

1993, 4, 959.

a) Wynberg, H.; Smaardijk, A.A. Tefruhedron Lezr. 1983, 24, 5899; b) Smaardijk, A.A.; Noorda, S.; van Bolhuis, F.; Wynberg, H. Tetrahedron Lett. 1985, 26, 493; c) Yokomatsu, T.; Yamagishi, T.; Shibuya, S. Tetrahedron: Asymmet?y 1993,4, 1779; d) Yokomatsu, T.; Yamagishi, T.; Shibuya, S. Tetrahedron: Asymmetry 1993,4, 1783; e) Rath, N.P.; Spilling, C.D. Tetrahedron Lett. 1994,35, 227.

6.

a) Sum, V.; Kee, T.P. J. Chem. Sac. Perkin Trans. I 1993,270l;

b) Sum, V.; Kee, T.P.; Thornton-

T. GAJDA

1972

Pea, M. J. Chem. Sot., Chem. Co-. Tetrahedron: Asymmet~

1994, 743; c) Blazis, V.J.; Koeller, K.J.; Spilling, C.D.

1994, 5, 499; d) Blazis, V.B.; De la Cruz, A.; Koeller, K.J.; Spilling, C.D.

Phosphorus, Susfur, and Silicon 1993, 75, 159. 7.

For reduction of diethyl benzoylphosphonate with stoichiometric amount of complex chiral borohydrides see: Creary, X.; Geiger, C.C. ; Hilton, K. J. Am. Chem. Sot. 1983,105,2851;

The configuration and

enantiomeric purity of the diethyl et-hydroxyphosphonate was not determined. 8.

Recent review: Sing, V.K. Synthesis 1992, 605; Wallbaum, S.; Martens, J. Tetrahedron: Asymmetry 1992, 3, 1475; Deloux, L.; Srebnik, M. Chem. Rev. 1993, 93, 763.

9.

Berlin, K.D. ; Ray, N.K.; Claunch, R.T. J. Am. Chem. Sot. 1968, 90, 4494.

10.

Corey, E.J.; Link, J.O. J. Am. Chem. Sot. 1992, 114, 1906.

11.

a) Huber, R.; Knierzinger,

A; Obrecht, J-P.; Vasella, A. Heiv. Chim. Acta 1985, 68, 1730; b)

Glowacki, Z.: Hoffmann, M. Phosphorus, Su(fur, and Silicon 1991, 55, 169; c) Hulst, R.; de Vries, N.K.; Feringa, B.L. Tetrahedron: Asymmetry 1994,5, 699, and references cited therein. 12.

Corey, E.J.; Bakshi, R.K.; Shibata, S. J. Am. Chem. Sot. 1987, 109, 5551; Corey, E.J.; Bakshi, R.K.; Shibata, S.; Chen, C-P.; Singh, V.K. ibid 1987, 109, 7925.

13.

Gajda, T.; Matusiak. M. Synth. Comnuua. 1992, 22, 2193; Gajda, T.; Matusiak, M. Phosphonrs, Sulfur, and Silicon 1993, 77, 192.

14. 15.

Gajda, T. Phosphorus, Su&u, and Silicon 1993, 85, 59.

For review see: Mitaunobu, 0. Synthesis 1981, 1; Hughes, D.L. Organic Reactions, ed. Paquette, L.A. et al.; John Wiley and Sons Inc.; New York-Chichester-Brisbane-Toronto-Singapore

16.

Review: Gololobov, Y.G.; Kasukhin, L.F. Tetrahedron 1992,48, 1353.

17.

a) Jommi, G.; Miglierini, G.; Pagliarin, R.; Sello, G.; Sisti, M. Tctmhedron:Asymmet~

1992, 42, 335.

1992,3, 1131

; b) Schbllkopf, U.; Schutze, R.; Liebigs Ann. Chem. 1987, 45; c) Las&at, S.; Kunz, K. synthesis l!w2,90. 18.

Reviews: Dhawan, B.; Redmore, D. Phosphorus and St&r

1987,32,

119; Kukhar, V.P.; Svistunova,

N.Yu.; Solodenko, V.A.; Soloshonok, V.A. Usp. Khim 1993, 62, 284; Russ. C&em. Rev. 1993, 62, 261, and references cited therein; recent works: Maury, C.; Royer, J.; Husson, H-P. Tetrahedron Lett. 1992,33, 6127; Hanessian, S.; Bennani, Y-L.; Herve, Y. Synfett 1993,35; Jacquier, R.; Lhassani, M.; Petrus, C.; Petrus, F. Phosphonu,

Suifiu, and Silicon 1993,81, 83; Groth, U.; Lehmann, L.; Richter,

L.; Schollkopf, U. Liebigs Ann. Chem. 1993, 427; ref. lb, 17. 19.

Rabjohn, N. Org. Synth. Coil. Vol III 1955, 375.

20.

Wolf, H. Organic Reactions, ed. Adams, R.; John Wiley and Sons.; New York. 1947, 3, 327.

(Received in UK 14 July 1994; accepted 22 August 1994)