S. Chandrasekhar et al. / Tetrahedron Letters 47 (2006) 7307–7309
7309
6. (a) Chandrasekhar, S.; Ramachander, T.; Venkateswara
Rao, B. Tetrahedron: Asymmetry 2001, 12, 2315–2321; (b)
Ravi Kumar, A.; Venkateswara Rao, B. Tetrahedron Lett.
2003, 44, 5645–5647.
7. (a) Thoen, J. C.; Morales-Ramos, A.; Lipton, M. A. Org.
Lett. 2002, 4, 4455–4458; (b) Jongho, J. H.; Suk-Koo, H.;
Joon, S. O.; Young, G. K. J. Org. Chem. 2006, 71, 3310–
3313.
which was esterified as its methyl ester 18 using ethereal
diazomethane.
Finally, the azide in 18 was reduced using Pd–CaCO3/
H2 to give the amine, which was protected as its Cbz
derivative using CbzCl in the presence of DIPEA to fur-
nish the protected (2R,3R,4S)-4,7-diamino-2,3-dihydr-
oxyheptanoic acid 19 in acceptable yield, which was
confirmed by routine spectral analyses.12
8. Ermolenko, L.; Sasaki, N. A. J. Org. Chem. 2006, 71, 693–
703.
9. Chan, T. H.; Li, C. J. Can. J. Chem. 1992, 70, 2726–
2729.
In conclusion, we have developed an efficient synthetic
approach for the preparation of a protected form of the
unusual amino acid fragment 19 of callipeltins A and D.
It is to be noted that the protected amino acid fragment
of callipeltin A was achieved in fewer steps in the current
approach, when compared to our earlier approach.6a
10. (a) Rychnovsky, S. D.; Skalitzky, D. J. Tetrahedron Lett.
1990, 31, 945–948; (b) Evans, D. A.; Rieger, D. L.; Gage,
J. R. Tetrahedron Lett. 1990, 31, 7099–7100; (c) Rych-
novsky, S. D.; Roger, B. N.; Richardson, T. I. Acc. Chem.
Res. 1998, 31, 9–17.
11. (a) Einhorn, J.; Einhorn, C.; Ratajczak, F.; Pierre, J. L.
J. Org. Chem. 1996, 61, 7452–7454; (b) Dalcanale, E.;
Montanari, F. J. Org. Chem. 1986, 51, 567–569.
12. The spectral data for selected compounds: compound 13
Acknowledgment
25
½aꢀD ꢁ15.8 (c 1.0, CHCl3). IR (KBr): 3414, 2986, 2111,
1
1618, 1375, 1217, 1073, and 769 cmꢁ1. H NMR (CDCl3,
M.S.R. and G.S.K. thank CSIR, New Delhi for the
financial support in the form of fellowships.
300 MHz): d 7.38–7.23 (m, 5H), 5.83–5.68 (m, 1H),
5.18–5.10 (m, 2H), 4.74 (d, J = 11.3 Hz, 1H), 4.64 (d,
J = 11.3 Hz, 1H), 4.14 (q, J = 6.04, 1H), 4.04 (dd,
J = 8.30, 6.04 Hz, 1H), 3.88 (dd, J = 8.30, 6.04 Hz, 1H),
3.60 (dd, J = 5.28, 2.28 Hz, 1H), 3.26 (dt, J = 6.79,
3.02 Hz, 1H), 2.57–2.36 (m, 2H), 1.38 (s, 3H), 1.33 (s,
3H). 13C NMR (50 MHz, CDCl3): d 137.7, 133.6, 128.4,
127.8, 127.6, 118.5, 108.8, 80.5, 74.9, 66.2, 61.7, 34.8,
23.5, and 24.2. ESI-MS: m/z 340 (M+Na)+.
References and notes
1. Ireland, C. M.; Molinski, T. F.; Roll, D. M.; Zabriskie, T.
M.; McKee, T. C.; Swersey, J. C.; Foster, M. P. In
Bioorganic Marine Chemistry; Scheuer, P. J., Ed.;
Springer: Berlin, Heidelberg, 1989; pp 1–46.
2. Zampella, A.; Valeria D’Auria, M.; Gomez Paloma, L.
J. Am. Chem. Soc. 1996, 118, 6202–6209.
25
Compound 19: ½aꢀD ꢁ31.2 (c 0.4 CHCl3). IR (KBr):
1
3418, 2928, 1704, 1364, 1248, 1165, 788 cmꢁ1. H NMR
3. Zampella, A.; Randazzo, A.; Borbone, N.; Luciani, S.;
Trevisi, L.; Debitus, C.; D’Auria, M. V. Tetrahedron Lett.
2002, 43, 6163–6166.
4. D’Auria, M. V.; Zampella, A.; Paloma, L. G.; Minale, L.;
Debitus, C.; Roussakis, C.; Le Bert, V. Tetrahedron 1996,
52, 9589–9596.
5. Trevisi, L.; Bova, S.; Cargnelli, G.; Danieli-Betto, D.;
Floreani, M.; Germinario, E.; D’Auria, M. V.; Luciani, S.
Biochem. Biophys. Res. Commun. 2000, 279, 219–222.
(CDCl3, 300 MHz): d 7.42–7.26 (m, 10H), 5.09 (s, 2H),
4.82–4.70 (m, 2H), 4.59 (d, J = 10.6 Hz, 1H), 4.46
(d, J = 10.6 Hz, 1H), 4.12 (d, J = 8.30 Hz, 1H), 3.96–
3.85 (m, 1H), 3.77 (s, 3H), 3.64 (d, J = 8.30 Hz, 1H),
3.24–3.09 (m, 3H), 1.56–1.37 (m, 13H). 13C NMR
(50 MHz, CDCl3): d 173.0, 156.9, 156.4, 137.4, 136.5,
128.5, 128.2, 128.1, 81.6, 80.2, 74.5, 71.0, 66.6, 52.4, 50.7,
40.6, 30.3, 29.5, 28.3, and 26.8. ESI-MS: m/z 553
(M+Na)+, 530 (M)+.