A process for the preparation of estra-1,3,5 -trien-3,15α,16α,17β-tetraol I which comprises the steps of: conversion of estrone II into 17-B-oxy-3-A-oxy-estra-1,3,5,16-tetraene III, wherein A is a protecting group and B is -Si(R 2) 3; conversion of 17-B-oxy-3-A-oxy-estra-1,3,5,16-tetraene III into 3-A-oxy-estra-1,3,5,15-tetraen-17-one IV, wherein A is a protecting group; reduction of the 17-keto group of 3-A-oxy-estra-1,3,5,15-tetraen-17-one IV to form 3-A-oxy-estra-1,3,5,15-tetraen-17β-ol V, wherein A is a protecting group; protection of the 17-OH group of 3-A-oxy-estra-1,3,5,15-tetraen-17β-ol V to form 3-A-oxy-17-C-oxy-estra-1,3,5,15-tetraene VI, wherein A and C are protecting groups; oxidation of the carbon-carbon double bond of ring D of 3-A-oxy-17-C-oxy-estra-1,3,5,15-tetraene VI to form protected estetrol VII, wherein A and C are protecting groups; and removal of protecting groups A and C to form estetrol I; wherein: A is a protecting group selected from the group consisting of a C 1 -C 5 alkyl group, a C 7 - C 12 benzylic group and a -Si(R 1) 3 group, wherein R 1 is independently selected from the group consisting of a C 1 - C 6 alkyl group and a C 6 - C 12 aryl group; B is -Si(R 2) 3, wherein R 2 is independently selected from the group consisting of a C 1 - C 6 alkyl group and a C 6 - C 12 aryl group; wherein alkyl includes also cyclopropyl, cyclobutyl, cyclopentyl, methylcyclobutyl and cyclohexyl; and C is a protecting group selected from the group consisting of monofunctional protecting groups that are suitable for the protection of an aliphatic hydroxyl group; and wherein step of the process is performed in the presence of an iodine species; or wherein step of the process is performed in the presence of a transition metal compound, and wherein the transition metal compound is present in an amount of 0.1 mol% to 50 mol% with respect to compound III. conversion of estrone II into 17-B-oxy-3-A-oxy-estra-1,3,5,16-tetraene III, wherein A is a protecting group and B is -Si(R 2) 3; conversion of 17-B-oxy-3-A-oxy-estra-1,3,5,16-tetraene III into 3-A-oxy-estra-1,3,5,15-tetraen-17-one IV, wherein A is a protecting group; reduction of the 17-keto group of 3-A-oxy-estra-1,3,5,15-tetraen-17-one IV to form 3-A-oxy-estra-1,3,5,15-tetraen-17β-ol V, wherein A is a protecting group; protection of the 17-OH group of 3-A-oxy-estra-1,3,5,15-tetraen-17β-ol V to form 3-A-oxy-17-C-oxy-estra-1,3,5,15-tetraene VI, wherein A and C are protecting groups; oxidation of the carbon-carbon double bond of ring D of 3-A-oxy-17-C-oxy-estra-1,3,5,15-tetraene VI to form protected estetrol VII, wherein A and C are protecting groups; and removal of protecting groups A and C to form estetrol I; A is a protecting group selected from the group consisting of a C 1 -C 5 alkyl group, a C 7 - C 12 benzylic group and a -Si(R 1) 3 group, wherein R 1 is independently selected from the group consisting of a C 1 - C 6 alkyl group and a C 6 - C 12 aryl group; B is -Si(R 2) 3, wherein R 2 is independently selected from the group consisting of a C 1 - C 6 alkyl group and a C 6 - C 12 aryl group; wherein alkyl includes also cyclopropyl, cyclobutyl, cyclopentyl, methylcyclobutyl and cyclohexyl; and C is a protecting group selected from the group consisting of monofunctional protecting groups that are suitable for the protection of an aliphatic hydroxyl group; and wherein step of the process is performed in the presence of an iodine species; or wherein step of the process is performed in the presence of a transition metal compound, and wherein the transition metal compound is present in an amount of 0.1 mol% to 50 mol% with respect to compound III.