References and Notes
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Di Blasio B.
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<A NAME="RU04809ST-2">2</A> For a review on marine isocyanides
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Marrero-Ponce Y.
Iyarreta-Veitía M.
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Caine D.
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In the previous synthesis of (-)-gleenol,
the use of SuperQuat-type oxazolidine-2-one was necessary to minimize
the cleavage of the oxazolidin-2-one during the removal of chiral
auxiliary. Even employing SuperQuat, substantial amount of undesired
byproduct caused by the ring opening of SuperQuat was formed.
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Wu Y.
Yang Y.-Q.
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<A NAME="RU04809ST-10">10</A>
The absolute stereochemistry of (2S,3R)-aldol
adduct 6 was established by comparison
of the specific rotation of the primary alcohol derived from ester 7.
<A NAME="RU04809ST-11">11</A>
An SN2 reaction of tosylate 16a prepared from axenol 4 with potassium
azide has been reported by Caine and co-workers (Scheme
[4]
).
[5]
However,
we were unable to observe the formation of tosylate 16a using
their protocol. Thus we chose mesylate as an alternative leaving
group. Unfortunately, azidation of 16b under
various reaction conditions (i.e., NaN3, 15-crown-5,
benzene, 80 ˚C; NaN3, DMF, 100 ˚C;
aq LiN3, DMF, 100 ˚C; n-Bu4NCl,
NaN3, NMP, 60 ˚C) was found to be unsuccessful.
In each case, only a trace amount of the desired azide 17 was detected. Therefore we chose an
alternative approach as shown in Scheme
[³]
.
<A NAME="RU04809ST-12A">12a</A>
Reisman SE.
Ready JM.
Hasuoka A.
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<A NAME="RU04809ST-12B">12b</A>
Reisman SE.
Ready JM.
Weiss MM.
Hasuoka A.
Hirata M.
Tamaki K.
Ovaska TV.
Smith CJ.
Wood JL.
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<A NAME="RU04809ST-13">13</A>
NOESY analysis of O-methyl
oxime 18 indicated that 18 exists
predominantly as the chair conformer A at
r.t. in a CDCl3 solution, see Supporting Information.
Further, molecular mechanics calculations (SPARTAN) also supported
the above observation.
<A NAME="RU04809ST-14">14</A>
Spectral Data
for (+)-1
White solid; mp 94-95 ˚C; [α]D
²4 +54.4
(c 0.107, CHCl3); lit.
[¹]
[α]D +68.4
(c 1.0, CHCl3); lit.
[¹5]
[α]D +43.4
(c 0.006, CHCl3); R
f
= 0.45
(hexane-i-Pr2O = 20:1). ¹H
NMR (400 MHz, CDCl3): δ = 5.14 (q, J = 1.4 Hz,
1 H), 3.59 (br s, 1 H), 2.31-2.17 (m, 2 H), 2.01-1.90
(m, 2 H), 1.85-1.76 (m, 2 H), 1.74 (d, J = 1.4
Hz, 3 H), 1.59 (dqq, J = 9.4,
6.7, 6.7 Hz, 1 H), 1.51 (ddt, J = 13.4,
4.0, 3.5 Hz, 1 H), 1.33 (ddt, J = 12.8, 4.0,
13.4 Hz, 1 H), 1.20-1.11 (m, 1 H), 1.06 (ddt, J = 12.8, 4.0,
13.4 Hz, 1 H), 0.94 (d, J = 6.7
Hz, 3 H), 0.91 (d, J = 6.7 Hz,
3 H), 0.77 (d, J = 6.7
Hz, 3 H). ¹³C NMR (100 MHz, CDCl3): δ = 155.7,
144.8, 123.6, 64.5, 57.1, 43.8, 35.8, 34.9, 34.3, 31.2, 29.7, 24.9,
20.7, 20.3, 16.9, 16.1. IR (neat): 2925, 2131, 1541, 1456 cm-¹.
ESI-HRMS: m/z calcd for C16H26N: 232.2055;
found: 232.2059.
<A NAME="RU04809ST-15">15</A>
Jumaryatno P.
Stapleton BL.
Hooper JNA.
Brecknell DJ.
Blanchfield JT.
Garson MJ.
J. Nat. Prod.
2007,
70:
1725
