Triterpene saponins, methods of synthesis and uses thereof

A compound of formula II-b:

• or a pharmaceutically acceptable salt thereof, wherein:
• is a single or double bond;
• W is Me, —CHO,
• —CH2ORx, or —C(O)Ry;
• V is hydrogen or —ORx;
• each occurrence of Rx is independently hydrogen or an oxygen protecting group selected from the group consisting of alkyl ethers, benzyl ethers, silyl ethers, acetals, ketals, esters, carbamates, and carbonates;
• RY is —OH, —OR, or a carboxyl protecting group selected from the group consisting of ester, amides, and hydrazides;
• Rs is
• each occurrence of Rx′ is independently an optionally substituted group selected from 6-10-membered aryl, C1-6 aliphatic, or C1-6 heteroaliphatic having 1-2 heteroatoms
• independently elected from the group consisting of nitrogen, oxygen, and sulfur;
• or:
• two Rx′ are taken together to form a 5-7-membered heterocyclic ring having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur;
• each occurrence of R is independently hydrogen, an optionally substituted group selected from acyl, arylalkyl, 6-10-membered aryl, C1-12 aliphatic, or C1-12 heteroaliphatic having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur;
• or:
• two R on the same nitrogen atom are taken with the nitrogen to form a 4-7-membered heterocyclic ring having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur;
• each occurrence of R1 is Rx or a carbohydrate domain having the structure:
• wherein:
• each occurrence of a, b, and c is independently 0, 1, or 2;
• d is an integer from 1-5, wherein each d bracketed structure may be the same or different;
• with the proviso that the d bracketed structure represents a furanose or pyranose moiety, and the sum of b and c is 1 or 2;
• R0 is hydrogen, an oxygen protecting group selected from the group consisting of alkyl ethers, benzyl ethers, silyl ethers, acetals, ketals, esters, carbamates, and carbonates;
• or an optionally substituted moiety selected from the group consisting of acyl, C1-10 aliphatic, C1-6 heteroaliphatic, 6-10-membered aryl, arylalkyl, 5-10-membered heteroaryl having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, 4-7-membered heterocyclyl having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur;
• R3 is hydrogen, halogen, CH2OR, or an optionally substituted group selected from the group consisting of acyl, C1-10 aliphatic, C1-6 heteroaliphatic, 6-10-membered aryl, arylalkyl, 5-10-membered heteroaryl having 1-4 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur;
• 4-7-membered heterocyclyl having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur;
• with the proviso that R3 is not methyl;
• R4 is
• wherein X is —O— or —NR—;
• or
• T-Rz, wherein:
• T is a covalent bond or a bivalent C1-26 saturated or unsaturated, straight or branched, aliphatic or heteroaliphatic chain;
• and
• Rz is hydrogen, halogen, —OR, —ORx, —OR1, —SR, —NR2, —NC(O)OR, or an optionally substituted group selected from acyl, arylalkyl, heteroarylalkyl, C1-6 aliphatic, 6-10-membered aryl, 5-10-membered heteroaryl having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, 4-7-membered heterocyclyl having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen and sulfur;
• or
• two R4 on the same nitrogen atom are taken with the nitrogen to form a 4-7-membered heterocyclic ring having 1-2 heteroatoms independently selected from the group consisting of nitrogen, oxygen, and sulfur.