Abstract: An erythromycin A derivative represented by the formula (I): ##STR1## ?wherein R.sup.1 is a group represented by the formula: --OCOCH.sub.2 Y (wherein Y is a pyridyl group, a quinolyl group, a p-nitrophenyl group or a group represented by the formula: --NR.sup.4 R.sup.5 (wherein R.sup.4 and R.sup.5 may be the same or different, and are each a hydrogen atom, a methyl group, a pyridylmethyl, a quinolylmethyl group or a benzyloxycarbonyl group)) or a cladinosyloxy group, R.sup.2 is a hydrogen atom, or R.sup.1 and R.sup.2 together form an oxo group, R.sup.3 is a hydrogen atom, an acetyl group, an ethylsuccinyl group or a nicotinoyl group! or a pharmaceutically acceptable salt thereof has a strong antibacterial activity against not only Gram-positive bacteria but also some Gram-negative bacteria, in particular, Haemophilus influenzae which is a serious factor of infectious diseases in the respiratory organs.

Abstract: Object: To provide novel macrolide antibiotics having a strong antibacterial activity. Constitution: 5-O-desosaminylerythronolide A derivatives represented by the formula: ##STR1## [wherein -A- - is a group of --N(R.sup.3)-- (wherein R.sup.3 is a hydrogen atom or an alkyl group having 1-3 carbon atoms) or a group represented by --N.dbd., and R.sup.1 and R.sup.2 are each a hydrogen atom or an alkyl group having 1-3 carbon atoms] which is a tricyclic carbamate of 5-0-desosaminylerythronolide A derivative having a ketone at the 3-position, being substituted by a methoxy group at the 6-position, and a pharmaceutically acceptable acid addition salt thereof; and a compound represented by the formula: ##STR2## (wherein R.sup.4 is an acetyl group or a propionyl group) which is an intermediate useful for the preparation of the 3-ketone forms of 5-O-desosaminylerythronolide A derivatives.

Abstract: Object:Provision of novel macrolide antibiotics having a strong antibacterial activity.Construction:Compounds represented by the formula: ##STR1## which are obtained by introducing a certain substituted carbonyloxy group into 5-O-desosaminylerythronolide derivatives at the 3-position; and pharmaceutically acceptable acid addition salts thereof.

Abstract: A novel macloride antibiotic having a potent antibacterial activity, represented by the formula: ##STR1## which is obtained by introducing a specific aryloxy or alkoxy group into the 3-position of a 5-O-desosaminylerythronolide derivative; or phamaceutically acceptable acid addition salts thereof.

Abstract: Object: To provide a novel macrolide antibiotic having a strong antibacterial activity.Constitution: 11-Amino-3,11-dideoxy-3-oxo-5-O-desosaminyl-6-O-methylerythronolide A 11-N,12-O-cyclic carbamate which has a ketone at the 3-position and a methylated hydroxyl group at the 6-position of a 5-O-desosaminylerythronolide A derivative, and pharmaceutically acceptable acid addition salts thereof.

Abstract: Provision of novel macrolide antibiotics having a strong antibacterial activity.Construction:Compounds represented by the formula: ##STR1## which are obtained by introducing a carbamoyl group into 5-O-desosaminyl-6-O-methylerythronolide derivatives at the 3-position; and pharmaceutically acceptable acid addition salts thereof.

Abstract: This invention provides 6-O-methylerythromycin A derivatives represented by the following formula ##STR1## (wherein R.sup.1 and R.sup.2 each represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and A represents a nitrogen atom or a N.fwdarw.O group) and their pharmaceutically acceptable salts. The erythromycin A derivatives have a strong antimicrobial activity against Gram-negative bacteria and have a much stronger activity against Gram-positive bacteria than previously known compounds.

Abstract: Erythromycins showing an extremely relieved bitterness at administration and an improved absorbability in vivo when orally administered are provided.A compound having a group represented by the following formula:--O--CO--O--[(CH.sub.2).sub.m --O].sub.n --R(wherein R represents an alkyl group having from 1 to 12 carbon atoms, m represents an integer of from 2 to 4, and n represents an integer of from 1 to 7) at the 2'-position of erythromycins or a salt thereof.

Abstract: A 6-O-methylerythromycin A oxime derivative represented by the formula ##STR1## wherein X is a substituted benzyl group, a substituted phenyl group, an .alpha.-methylbenzyl group, an .alpha.-methylphenethyl group, a diphenylmethyl group, a trityl group, a dibenzosuberanyl group, or a group of the formula --(CH.sub.2).sub.n --R, and Y is a hydrogen atom, a substituted phenyl group or a 2-aminothiazol-4-ylmethylcarbonyl group, and a pharmaceutically acceptable salt thereof are disclosed. These compounds have antibacterial activity against erythromycin resistant bacteria.

Abstract: Erthromycin A derivatives represented by the general formula ##STR1## wherein R.sup.1 is a group of the formula R.sup.7 CH.sub.2 -- (wherein R.sup.7 is a hydrogen group or a lower alkyl group) or a group of the formula R.sup.8 O-- (wherein R.sup.8 is a lower alkyl group), R.sup.2 is R.sup.8, a cycloalkyl group, a phenyl group or an aralkyl group.), or R.sup.2 and R.sup.7 together form an alkylene group, R.sup.3 is a hydrogen atom, a lower alkyl group, a phenyl group or an aralkyl group, or R.sup.3 and R.sup.7 together form an alkylene group, or R.sup.2 and R.sup.3 together form an alkylene group, R.sup.4 is a lower alkyl group, R.sup.5 is a substituted silyl group, and R.sup.6 is a hydrogen atom or R.sup.5, are disclosed. These compounds are useful as intermediates for the synthesis of antibacterial agents.

Abstract: A method for the selective methylation of the hydroxy group at the 6-position of erythromycin A derivatives which comprises reacting a compound represented by the formula R-X (wherein R is a 2-alkenyl group, a benzyl group or a substituted benzyl group, and X is a halogen atom), reacting the resulting quaternary salt compound with a methylating agent, and then eliminating R groups of the resulting compound to give 6-O-methylerythromycin A 9-oxime, is disclosed.