6189. Milbemectin
Nomenclature
E-187; Koromite (Sankyo); Milbeknock (Sankyo).Description and references
Mixture of milbemycins, q.v, in a 3:7 ratio of milbemycin A3 and milbemycin A4. Isolated from fermentation broth of Streptomyces hygroscopicus subsp. aureolacrimosus SANK60576; structurally related to the avermectins, q.v.: A. Aoki et al., DE 2329486; eidem, US 3950360 (1973, 1976 both to Sankyo); Y. Takiguchi et al., J. Antibiot. 33, 1120 (1980). Synthesis of A3: M. Hirama et al., J. Am. Chem. Soc. 113, 1830 (1991); S. V. Ley et al., Tetrahedron Lett. 34, 7479 (1993). Metabolism in rats: S. Sadakane et al., J. Pestic. Sci. 17, 147 (1992). Review: A. Aoki et al., ibid. 19, 245-247 (1994).
Properties
Stable to heat; relatively unstable under direct sunlight. Relatively unstable to acid; unstable to alkali. LD50 in male, female rats, mice (mg/kg): 762, 456, 324, 313 orally; in rats (mg/kg): >5000 dermally (Aoki, 1994). LC50 by inhalation in male, female rats (mg/l): 1.90, 2.80 (Aoki, 1994).Derivative
Milbemycin A3.Nomenclature
CAS number: 51596-10-2
(6R,25R)-5-O-Demethyl-28-deoxy-6,28-epoxy-25-methylmilbemycin; milbemycin α1; antibiotic B-41A3. C31H44O7; mol wt 528.68.
C 70.43%, H 8.39%, O 21.18%.
Properties
White crystalline powder, mp 212-215°. [α]D20 +106° (c = 0.25 in acetone) (Aoki). Also reported as mp 192-194°. [α]D20 +106° (acetone) (Hirama). uv max (ethanol): 238, 244 nm (ε 27800, 30500). Soly in water (20°): 7.2 ppm; methanol 64.8 g/l; ethanol 41.9 g/l; acetone 66.1 g/l; n-hexane 1.4 g/l; benzene 143.1 g/l; ethyl acetate 69.5 g/l. Vapor pressure (20°): <1 × 1010 mm Hg.Derivative
Milbemycin A4.Nomenclature
CAS number: 51596-11-3
Milbemycin α3; antibiotic B-41A4. C32H46O7; mol wt 542.70.
C 70.82%, H 8.54%, O 20.64%.