(3aR,5R,7S,7aS)-5-[(tert-But­yldimeth­ylsil­yloxy)meth­yl]-7-eth­oxy-3-methyl-7,7a-dihydro-3aH-pyrano[4,3-d]isoxazol-4(5H)-one

The title compound, C₁₆H₂₉NO₅Si, is a unique heterocyclic compound where the 3-methyl-4,5-dihydro­isoxazole (3-methyl-Δ²-isoxazoline) ring has a tetra­hydro­pyran-4-one group fused to the five-membered heterocyclic ring. This bicyclic heterocycle has four asymmetric centers with well defined configurations at all stereocenters.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.046
• wR factor = 0.047
• Data-to-parameter ratio = 7.9

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT222_ALERT_3_B Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       4.03 Ratio

Alert level C
ABSTM02_ALERT_3_C  The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
            Tmin and Tmax reported:      0.780     1.000
            Tmin(prime) and Tmax expected:      0.994     0.997
            RR(prime) =      0.782
            Please check that your absorption correction is appropriate.
REFNR01_ALERT_3_C  Ratio of reflections to parameters is < 8 for a
            non-centrosymmetric structure, where ZMAX < 18
            sine(theta)/lambda                0.6481
            Proportion of unique data used    0.6897
            Ratio reflections to parameters   7.9183
PLAT022_ALERT_3_C Ratio Unique / Expected Reflections too Low ....       0.94
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.97
PLAT061_ALERT_3_C Tmax/Tmin Range Test RR' too Large .............       0.78
PLAT089_ALERT_3_C Poor Data / Parameter Ratio (Zmax .LT. 18) .....       7.92
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       3.02 Ratio
PLAT230_ALERT_2_C Hirshfeld Test Diff for    N      -   C8      ..       5.21 su
PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          6
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          1
              C16 H29 N O5 Si

Alert level G
REFLT03_ALERT_4_G  WARNING: Large fraction of Friedel related reflns may
                     be needed to determine absolute structure
           From the CIF: _diffrn_reflns_theta_max           27.43
           From the CIF: _reflns_number_total               2388
           Count of symmetry unique reflns         2532
           Completeness (_total/calc)             94.31%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present        yes

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
  10 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   8 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

---

Computing details

Data collection: COLLECT (Nonius, 2001); cell refinement: DENZO/SCALEPACK; data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: DIAMOND (Brandenburg & Putz, 1996); software used to prepare material for publication: CRYSTALS.

(3aR,5S,7S,7aS)-5-{[tert-Butyl(dimethyl)silyloxy]methyl}-7-ethoxy-3-methyl- 7,7a-dihydro-3aH-pyrano[4,3-d]isoxazol-4(5H)-one

Crystal data

C16H29NO5Si	Dx = 1.183 Mg m^−3
Mr = 343.49	Melting point: 90 K
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: P 2ac 2ab	Cell parameters from 2082 reflections
a = 7.366 (5) Å	θ = 1.0–27.5°
b = 11.372 (5) Å	µ = 0.14 mm^−1
c = 23.020 (5) Å	T = 173 K
V = 1928.3 (16) Å^3	Needle, colorless
Z = 4	0.04 × 0.02 × 0.02 mm
F(000) = 744

Data collection

Nonius KappaCCD diffractometer	2388 independent reflections
Radiation source: fine-focus sealed tube	1647 reflections with I > 2σ(I)
Horizonally mounted graphite crystal monochromator	Rint = 0.049
Detector resolution: 9 pixels mm^-1	θmax = 27.4°, θmin = 1.8°
CCD scans	h = −9→8
Absorption correction: part of the refinement model (ΔF) (DIFABS; Walker & Stuart, 1983)	k = −14→14
Tmin = 0.78, Tmax = 1.00	l = −29→29
3739 measured reflections

Refinement

Refinement on F	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.048	H-atom parameters not refined
S = 1.06	Weighting scheme: Chebychev polynomial (Watkin, 1994; Prince, 1982): w = 1/[1.31T0(x)-0.0224T1(x) + 0.584T2(x) + 0.0446T3(x)], where x = F /Fmax; robust weighting (Prince, 1982): W = w[1-(δF/6σF)^2]^2
1647 reflections	(Δ/σ)max = 0.000192
208 parameters	Δρmax = 0.26 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

Special details

Experimental. Diffractometer equiped with an area detector. phi scans and omega scans during 20 s with 2 ° steps Crystal to detector distance: 27 mm

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

	x	y	z	Uiso*/Ueq
C1	−0.7716 (6)	0.0912 (4)	−1.03649 (17)	0.0411
C2	−0.6500 (5)	0.0990 (4)	−0.98468 (17)	0.0335
C3	−0.3594 (6)	0.0287 (4)	−0.95337 (17)	0.0327
C4	−0.2104 (6)	−0.0516 (4)	−0.97382 (16)	0.0383
C5	−0.2402 (6)	−0.1798 (4)	−0.95767 (15)	0.0317
C6	−0.4126 (6)	−0.2045 (4)	−0.92405 (16)	0.0277
C7	−0.4980 (5)	−0.1080 (3)	−0.88857 (14)	0.0232
C8	−0.0712 (6)	−0.2026 (4)	−0.92088 (17)	0.0301
C9	−0.0254 (7)	−0.3164 (4)	−0.8936 (2)	0.0461
C10	−0.4959 (6)	−0.1379 (3)	−0.82443 (15)	0.0271
C11	0.0310 (6)	−0.1150 (4)	−0.76247 (17)	0.0385
C12	−0.2864 (7)	0.0545 (3)	−0.7421 (2)	0.0435
C13	−0.2816 (6)	−0.1876 (4)	−0.68173 (16)	0.0342
C14	−0.4895 (7)	−0.1832 (4)	−0.6727 (2)	0.0493
C15	−0.1891 (10)	−0.1361 (5)	−0.62765 (19)	0.0697
C16	−0.2265 (8)	−0.3160 (4)	−0.6890 (2)	0.0523
O17	−0.5044 (4)	0.0151 (2)	−0.99268 (10)	0.0301
O18	−0.4086 (4)	0.0037 (2)	−0.89549 (10)	0.0269
O19	−0.4807 (4)	−0.3017 (3)	−0.92458 (13)	0.0429
O20	−0.0442 (4)	−0.0149 (3)	−0.94488 (15)	0.0496
O21	−0.3153 (4)	−0.1618 (2)	−0.80624 (11)	0.0275
N	0.0309 (5)	−0.1131 (4)	−0.91559 (15)	0.0409
Si	−0.21678 (14)	−0.10192 (8)	−0.74839 (4)	0.0239
H71	−0.6242	−0.1013	−0.9013	0.0265*
H101	−0.5705	−0.2087	−0.8182	0.0320*
H102	−0.5476	−0.0730	−0.8024	0.0322*
H41	−0.1943	−0.0429	−1.0159	0.0459*
H51	−0.2375	−0.2291	−0.9928	0.0364*
H21	−0.5985	0.1769	−0.9812	0.0402*
H22	−0.7161	0.0787	−0.9497	0.0398*
H31	−0.3163	0.1111	−0.9541	0.0377*
H111	0.0950	−0.0780	−0.7310	0.0541*
H112	0.0614	−0.0765	−0.7977	0.0539*
H113	0.0646	−0.1957	−0.7648	0.0544*
H141	−0.5230	−0.2278	−0.6389	0.0706*
H142	−0.5527	−0.2132	−0.7066	0.0705*
H143	−0.5237	−0.1022	−0.6667	0.0710*
H11	−0.8758	0.1418	−1.0304	0.0599*
H12	−0.7059	0.1153	−1.0705	0.0601*
H13	−0.8118	0.0109	−1.0417	0.0601*
H161	−0.2740	−0.3622	−0.6576	0.0758*
H162	−0.2739	−0.3455	−0.7251	0.0758*
H163	−0.0970	−0.3218	−0.6886	0.0761*
H91	−0.0318	−0.3773	−0.9228	0.0651*
H92	0.0957	−0.3137	−0.8778	0.0645*
H93	−0.1114	−0.3336	−0.8631	0.0648*
H121	−0.2117	0.0927	−0.7129	0.0618*
H122	−0.2696	0.0921	−0.7788	0.0623*
H123	−0.4122	0.0581	−0.7305	0.0618*
H151	−0.2209	−0.1824	−0.5941	0.1068*
H152	−0.0585	−0.1384	−0.6328	0.1068*
H153	−0.2262	−0.0555	−0.6218	0.1069*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.036 (2)	0.054 (3)	0.0334 (19)	0.009 (3)	0.0002 (19)	0.0116 (19)
C2	0.030 (2)	0.032 (2)	0.039 (2)	0.004 (2)	−0.0002 (17)	0.0004 (19)
C3	0.033 (2)	0.035 (2)	0.0300 (19)	−0.007 (2)	−0.0038 (17)	0.0021 (17)
C4	0.028 (2)	0.062 (3)	0.0257 (17)	0.006 (2)	0.0069 (18)	0.0067 (18)
C5	0.030 (2)	0.043 (2)	0.0226 (16)	0.009 (2)	−0.0017 (16)	−0.0083 (16)
C6	0.028 (2)	0.033 (2)	0.0224 (18)	0.006 (2)	−0.0100 (16)	−0.0030 (17)
C7	0.0156 (18)	0.0271 (18)	0.0269 (17)	−0.0033 (19)	−0.0010 (15)	−0.0045 (16)
C8	0.023 (2)	0.040 (3)	0.0271 (19)	0.010 (2)	0.0016 (16)	−0.0063 (19)
C9	0.043 (3)	0.048 (3)	0.047 (3)	0.016 (2)	−0.014 (2)	−0.011 (2)
C10	0.026 (2)	0.029 (2)	0.0259 (18)	−0.0032 (18)	0.0025 (17)	0.0004 (14)
C11	0.027 (2)	0.046 (2)	0.042 (2)	−0.005 (2)	−0.0011 (18)	0.001 (2)
C12	0.049 (3)	0.0269 (18)	0.055 (3)	0.001 (2)	−0.012 (3)	−0.0064 (19)
C13	0.043 (2)	0.037 (2)	0.0224 (16)	−0.013 (2)	−0.0007 (18)	−0.0022 (16)
C14	0.056 (3)	0.048 (3)	0.044 (3)	−0.014 (3)	0.020 (2)	−0.004 (2)
C15	0.103 (5)	0.081 (4)	0.025 (2)	−0.046 (4)	−0.014 (3)	0.006 (2)
C16	0.068 (3)	0.033 (2)	0.056 (3)	−0.003 (3)	−0.001 (3)	0.020 (2)
O17	0.0318 (15)	0.0335 (15)	0.0250 (12)	0.0070 (15)	−0.0039 (12)	0.0015 (11)
O18	0.0294 (15)	0.0262 (14)	0.0252 (13)	−0.0051 (13)	−0.0024 (11)	−0.0015 (11)
O19	0.0432 (19)	0.0332 (16)	0.0523 (18)	−0.0035 (16)	−0.0100 (16)	−0.0112 (14)
O20	0.0270 (17)	0.060 (2)	0.062 (2)	−0.0052 (16)	−0.0003 (15)	0.0249 (18)
O21	0.0274 (15)	0.0306 (14)	0.0244 (12)	0.0040 (13)	−0.0036 (12)	−0.0007 (10)
N	0.0273 (19)	0.058 (2)	0.0373 (18)	0.010 (2)	0.0002 (16)	0.0110 (19)
Si	0.0263 (5)	0.0201 (4)	0.0252 (4)	−0.0007 (5)	−0.0021 (5)	0.0000 (4)

Geometric parameters (Å, º)

C1—C2	1.494 (6)	C10—O21	1.420 (5)
C1—H11	0.970	C10—H101	0.985
C1—H12	0.960	C10—H102	0.973
C1—H13	0.968	C11—Si	1.860 (5)
C2—O17	1.447 (5)	C11—H111	0.961
C2—H21	0.966	C11—H112	0.949
C2—H22	0.969	C11—H113	0.953
C3—C4	1.503 (6)	C12—Si	1.857 (4)
C3—O17	1.408 (5)	C12—H121	0.971
C3—O18	1.410 (5)	C12—H122	0.956
C3—H31	0.989	C12—H123	0.965
C4—C5	1.520 (6)	C13—C14	1.546 (7)
C4—O20	1.455 (5)	C13—C15	1.535 (6)
C4—H41	0.981	C13—C16	1.524 (6)
C5—C6	1.513 (6)	C13—Si	1.879 (4)
C5—C8	1.528 (6)	C14—H141	0.963
C5—H51	0.986	C14—H142	0.971
C6—C7	1.505 (5)	C14—H143	0.964
C6—O19	1.214 (5)	C15—H151	0.964
C7—C10	1.515 (5)	C15—H152	0.970
C7—O18	1.439 (4)	C15—H153	0.966
C7—H71	0.978	C16—H161	0.959
C8—C9	1.478 (6)	C16—H162	0.962
C8—N	1.272 (6)	C16—H163	0.956
C9—H91	0.967	O20—N	1.417 (5)
C9—H92	0.964	O21—Si	1.663 (3)
C9—H93	0.965
C2—C1—H11	108.9	C7—C10—H102	109.5
C2—C1—H12	109.3	O21—C10—H102	111.0
H11—C1—H12	110.3	H101—C10—H102	109.0
C2—C1—H13	109.8	Si—C11—H111	108.4
H11—C1—H13	109.6	Si—C11—H112	110.1
H12—C1—H13	108.8	H111—C11—H112	109.0
C1—C2—O17	107.7 (3)	Si—C11—H113	110.0
C1—C2—H21	110.9	H111—C11—H113	109.7
O17—C2—H21	108.9	H112—C11—H113	109.6
C1—C2—H22	110.3	Si—C12—H121	109.1
O17—C2—H22	108.7	Si—C12—H122	108.9
H21—C2—H22	110.3	H121—C12—H122	109.8
C4—C3—O17	106.6 (3)	Si—C12—H123	109.1
C4—C3—O18	111.2 (3)	H121—C12—H123	109.6
O17—C3—O18	113.0 (3)	H122—C12—H123	110.4
C4—C3—H31	109.6	C14—C13—C15	108.5 (4)
O17—C3—H31	109.7	C14—C13—C16	108.0 (4)
O18—C3—H31	106.8	C15—C13—C16	109.7 (4)
C3—C4—C5	113.6 (4)	C14—C13—Si	110.1 (3)
C3—C4—O20	107.3 (3)	C15—C13—Si	110.6 (3)
C5—C4—O20	106.5 (3)	C16—C13—Si	109.9 (3)
C3—C4—H41	109.7	C13—C14—H141	110.2
C5—C4—H41	110.8	C13—C14—H142	110.8
O20—C4—H41	108.8	H141—C14—H142	110.1
C4—C5—C6	115.1 (3)	C13—C14—H143	108.0
C4—C5—C8	100.4 (4)	H141—C14—H143	108.6
C6—C5—C8	111.6 (3)	H142—C14—H143	109.0
C4—C5—H51	110.0	C13—C15—H151	109.5
C6—C5—H51	109.3	C13—C15—H152	109.3
C8—C5—H51	110.0	H151—C15—H152	108.9
C5—C6—C7	119.5 (3)	C13—C15—H153	110.5
C5—C6—O19	120.7 (4)	H151—C15—H153	109.7
C7—C6—O19	119.8 (4)	H152—C15—H153	108.8
C6—C7—C10	111.2 (3)	C13—C16—H161	110.2
C6—C7—O18	113.1 (3)	C13—C16—H162	109.4
C10—C7—O18	107.5 (3)	H161—C16—H162	109.1
C6—C7—H71	106.9	C13—C16—H163	109.3
C10—C7—H71	108.7	H161—C16—H163	108.6
O18—C7—H71	109.4	H162—C16—H163	110.2
C5—C8—C9	124.8 (4)	C2—O17—C3	114.1 (3)
C5—C8—N	113.5 (4)	C7—O18—C3	113.6 (3)
C9—C8—N	121.7 (4)	C4—O20—N	108.7 (3)
C8—C9—H91	108.6	C10—O21—Si	124.5 (2)
C8—C9—H92	110.1	O20—N—C8	110.8 (3)
H91—C9—H92	109.4	C13—Si—C11	110.5 (2)
C8—C9—H93	109.7	C13—Si—C12	111.3 (2)
H91—C9—H93	109.2	C11—Si—C12	111.2 (2)
H92—C9—H93	109.9	C13—Si—O21	109.31 (15)
C7—C10—O21	109.9 (3)	C11—Si—O21	104.85 (17)
C7—C10—H101	108.6	C12—Si—O21	109.54 (17)
O21—C10—H101	108.8