(2aRS,3RS,4aSR,6aRS,6bSR)-3-Hydr­oxy-2a,3,4a,6,6a,6b-hexa­hydro-1,4-dioxacyclo­penta­[cd]penta­len-2(5H)-one

The mol­ecular structure of the title compound [enanti­omers (VIII) and (VIIIa)], C₈H₁₀O₄, was determined in the course of our studies on the synthesis of cyclo­penta­[1,2-b]furan-4-one derivatives. Tricyclic (VIIIa) consists of a planar bridged lactone unit and the two other ring systems in the envelope conformation. It contains five chiral C atoms and was obtained as a racemic mixture. The X-ray analysis showed the compound to possess a half-acetal unit with an endo orientation of the half-acetal ether bridge with respect to the lactone unit.

Key indicators

• Single-crystal X-ray study
• T = 193 K
• Mean [sigma](C-C)= 0.002 Å
• R factor = 0.043
• wR factor = 0.112
• Data-to-parameter ratio = 12.7

checkCIF/PLATON results

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Computing details

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CORINC (Dräger & Gattow, 1971); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.

(VIII)

Crystal data

C8H10O4	F(000) = 360
Mr = 170.16	Dx = 1.525 Mg m^−3
Monoclinic, P21/c	Melting point: 126.0 K
Hall symbol: -P 2ybc	Cu Kα radiation, λ = 1.54178 Å
a = 9.7712 (6) Å	Cell parameters from 25 reflections
b = 10.0443 (3) Å	θ = 65–70°
c = 8.1779 (5) Å	µ = 1.05 mm^−1
β = 112.568 (3)°	T = 193 K
V = 741.16 (7) Å^3	Block, colourless
Z = 4	0.35 × 0.26 × 0.26 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	Rint = 0.034
Radiation source: rotating anode	θmax = 69.8°, θmin = 4.9°
Graphite monochromator	h = 0→11
ω/2θ scans	k = −12→0
1483 measured reflections	l = −9→9
1400 independent reflections	3 standard reflections every 60 min
1302 reflections with I > 2σ(I)	intensity decay: 5%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.043	H-atom parameters constrained
wR(F^2) = 0.112	w = 1/[σ^2(Fo^2) + (0.0625P)^2 + 0.3206P] where P = (Fo^2 + 2Fc^2)/3
S = 1.08	(Δ/σ)max = 0.001
1400 reflections	Δρmax = 0.34 e Å^−3
110 parameters	Δρmin = −0.23 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.029 (3)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.22900 (13)	0.14034 (11)	0.51424 (14)	0.0263 (3)
C2	0.23116 (17)	0.16649 (15)	0.69137 (19)	0.0234 (4)
H2A	0.2695	0.2579	0.7323	0.028*
C3	0.33282 (16)	0.05953 (14)	0.81407 (19)	0.0215 (4)
H3A	0.4196	0.0976	0.9138	0.026*
C4	0.23145 (17)	−0.02576 (15)	0.8762 (2)	0.0245 (4)
H4A	0.2827	−0.0564	1.0013	0.029*
O5	0.18835 (12)	−0.13574 (10)	0.75264 (15)	0.0250 (3)
C6	0.30770 (16)	−0.16615 (15)	0.7029 (2)	0.0227 (4)
H6A	0.2717	−0.2120	0.5854	0.027*
C7	0.37684 (16)	−0.03073 (14)	0.69193 (19)	0.0218 (4)
H7A	0.4869	−0.0368	0.7298	0.026*
C8	0.30422 (16)	0.03106 (15)	0.51041 (19)	0.0223 (4)
C9	0.07597 (18)	0.14778 (17)	0.6918 (2)	0.0294 (4)
H9A	0.0097	0.1047	0.5807	0.035*
H9B	0.0328	0.2347	0.7035	0.035*
C10	0.09631 (19)	0.05883 (16)	0.8514 (2)	0.0297 (4)
H10A	0.1128	0.1133	0.9582	0.036*
H10B	0.0079	0.0021	0.8281	0.036*
O11	0.41795 (12)	−0.24208 (11)	0.83091 (15)	0.0310 (3)
H11A	0.3785	−0.3130	0.8445	0.047*
O12	0.30800 (13)	−0.00944 (11)	0.37235 (14)	0.0288 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0360 (6)	0.0234 (6)	0.0219 (6)	0.0073 (4)	0.0136 (5)	0.0035 (4)
C2	0.0311 (8)	0.0194 (7)	0.0202 (7)	0.0014 (6)	0.0105 (6)	−0.0015 (5)
C3	0.0226 (7)	0.0203 (7)	0.0204 (7)	−0.0040 (6)	0.0068 (6)	−0.0001 (5)
C4	0.0310 (8)	0.0228 (8)	0.0220 (7)	−0.0052 (6)	0.0130 (6)	−0.0010 (6)
O5	0.0253 (6)	0.0208 (6)	0.0316 (6)	−0.0047 (4)	0.0140 (5)	−0.0033 (4)
C6	0.0243 (8)	0.0186 (7)	0.0263 (8)	0.0003 (5)	0.0109 (6)	0.0015 (6)
C7	0.0202 (7)	0.0205 (7)	0.0249 (7)	0.0005 (5)	0.0091 (6)	0.0023 (6)
C8	0.0239 (7)	0.0194 (7)	0.0262 (8)	−0.0024 (5)	0.0126 (6)	0.0008 (6)
C9	0.0274 (8)	0.0307 (8)	0.0300 (8)	0.0045 (6)	0.0110 (7)	−0.0047 (6)
C10	0.0333 (9)	0.0279 (8)	0.0347 (9)	−0.0048 (7)	0.0207 (7)	−0.0074 (6)
O11	0.0302 (6)	0.0214 (6)	0.0389 (7)	0.0025 (4)	0.0104 (5)	0.0094 (5)
O12	0.0381 (7)	0.0265 (6)	0.0280 (6)	0.0015 (5)	0.0194 (5)	−0.0004 (5)

Geometric parameters (Å, º)

O1—C8	1.3280 (18)	C6—O11	1.4045 (18)
O1—C2	1.4643 (17)	C6—C7	1.537 (2)
C2—C9	1.529 (2)	C6—H6A	1.0000
C2—C3	1.544 (2)	C7—C8	1.511 (2)
C2—H2A	1.0000	C7—H7A	1.0000
C3—C7	1.528 (2)	C8—O12	1.2140 (18)
C3—C4	1.536 (2)	C9—C10	1.531 (2)
C3—H3A	1.0000	C9—H9A	0.9900
C4—O5	1.4462 (18)	C9—H9B	0.9900
C4—C10	1.517 (2)	C10—H10A	0.9900
C4—H4A	1.0000	C10—H10B	0.9900
O5—C6	1.4083 (18)	O11—H11A	0.8375
C8—O1—C2	111.93 (11)	O5—C6—H6A	110.6
O1—C2—C9	110.01 (12)	C7—C6—H6A	110.6
O1—C2—C3	106.24 (11)	C8—C7—C3	104.75 (12)
C9—C2—C3	107.72 (12)	C8—C7—C6	111.69 (12)
O1—C2—H2A	110.9	C3—C7—C6	104.29 (11)
C9—C2—H2A	110.9	C8—C7—H7A	111.9
C3—C2—H2A	110.9	C3—C7—H7A	111.9
C7—C3—C4	105.32 (12)	C6—C7—H7A	111.9
C7—C3—C2	105.09 (11)	O12—C8—O1	120.90 (14)
C4—C3—C2	105.51 (12)	O12—C8—C7	127.27 (14)
C7—C3—H3A	113.4	O1—C8—C7	111.82 (12)
C4—C3—H3A	113.4	C2—C9—C10	105.62 (13)
C2—C3—H3A	113.4	C2—C9—H9A	110.6
O5—C4—C10	109.23 (12)	C10—C9—H9A	110.6
O5—C4—C3	104.30 (11)	C2—C9—H9B	110.6
C10—C4—C3	106.40 (13)	C10—C9—H9B	110.6
O5—C4—H4A	112.2	H9A—C9—H9B	108.7
C10—C4—H4A	112.2	C4—C10—C9	105.19 (12)
C3—C4—H4A	112.2	C4—C10—H10A	110.7
C6—O5—C4	108.42 (11)	C9—C10—H10A	110.7
O11—C6—O5	112.69 (12)	C4—C10—H10B	110.7
O11—C6—C7	107.19 (12)	C9—C10—H10B	110.7
O5—C6—C7	104.84 (11)	H10A—C10—H10B	108.8
O11—C6—H6A	110.6	C6—O11—H11A	107.5
C8—O1—C2—C9	−112.17 (14)	C2—C3—C7—C6	−115.45 (12)
C8—O1—C2—C3	4.15 (16)	O11—C6—C7—C8	151.85 (12)
O1—C2—C3—C7	−3.63 (15)	O5—C6—C7—C8	−88.17 (14)
C9—C2—C3—C7	114.22 (13)	O11—C6—C7—C3	−95.56 (13)
O1—C2—C3—C4	−114.66 (13)	O5—C6—C7—C3	24.42 (14)
C9—C2—C3—C4	3.19 (15)	C2—O1—C8—O12	176.31 (13)
C7—C3—C4—O5	−16.61 (15)	C2—O1—C8—C7	−2.93 (16)
C2—C3—C4—O5	94.26 (13)	C3—C7—C8—O12	−178.76 (14)
C7—C3—C4—C10	−132.04 (13)	C6—C7—C8—O12	−66.46 (19)
C2—C3—C4—C10	−21.17 (15)	C3—C7—C8—O1	0.43 (16)
C10—C4—O5—C6	147.30 (12)	C6—C7—C8—O1	112.73 (14)
C3—C4—O5—C6	33.88 (15)	O1—C2—C9—C10	131.10 (12)
C4—O5—C6—O11	79.32 (14)	C3—C2—C9—C10	15.71 (16)
C4—O5—C6—C7	−36.93 (14)	O5—C4—C10—C9	−80.91 (14)
C4—C3—C7—C8	113.19 (12)	C3—C4—C10—C9	31.14 (16)
C2—C3—C7—C8	2.03 (14)	C2—C9—C10—C4	−28.79 (16)
C4—C3—C7—C6	−4.29 (15)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O11—H11A···O12^i	0.84	1.96	2.7888 (16)	173

Symmetry code: (i) x, −y−1/2, z+1/2.